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←Created page with '{{Infobox academic | name = Helen Greenwood Hansma | image = | birth_date = | birth_place = | nationality =American | occupation = Biologist, biophysicist, biochemist, and academic | title = | awards = | website = | education =B.S. in Chemistry<br>M.S. in Biochemistry<br>PhD in Biological Sciences | alma_mater = Earl...'
 
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| workplaces = University of California, Santa Barbara<br>[[University of California, Los Angeles|UCLA]] [post doc]
| workplaces = University of California, Santa Barbara<br>[[University of California, Los Angeles|UCLA]] [post doc]
}}
}}
'''Helen Greenwood Hansma''' is an [[Americans|American]] [[biologist]], [[biophysics|biophysicist]], [[biochemist]], and academic. She is a Researcher Emeritus and Associate Adjunct Professor [[Emeritus]] at the [[University of California, Santa Barbara]].<ref name=aaa>{{cite web|url=https://awis.org/project/helen-greenwood-hansma-phd/|title=AWIS Member Spotlight: Helen Greenwood Hansma, PhD }}</ref>
'''Helen Greenwood Hansma''' is an [[Americans|American]] [[biologist]], [[biophysics|biophysicist]], [[biochemist]], and academic. She is a Researcher Emeritus and Associate Adjunct Professor [[Emeritus]] at the [[University of California, Santa Barbara]].<ref name=aaa>{{Cite web|url=https://awis.org/project/helen-greenwood-hansma-phd/|title=AWIS Member Spotlight: Helen Greenwood Hansma, PhD|date=January 18, 2023|website=AWIS}}</ref>


Hansma’s research revolves around understanding the origin of life and proposes that life originated between [[mica]] sheets in micaceous clay.<ref>{{cite web|url=https://www.cell.com/biophysj/fulltext/S0006-3495(22)00692-0#%20|title=DNA and the origins of life in micaceous clay}}</ref> She has contributed to the fields of biophysics and [[biochemistry]] through her work on [[biomolecule|biomolecular materials]], DNA-protein interactions, and the applications of [[Atomic Force Microscopy]] to biological materials.
Hansma’s research revolves around understanding the origin of life and proposes that life originated between [[mica]] sheets in micaceous clay.<ref>{{Cite web|url=https://www.cell.com/biophysj/fulltext/S0006-3495(22)00692-0#%20|title=DNA and the origins of life in micaceous clay: Biophysical Journal}}</ref> She has contributed to the fields of biophysics and [[biochemistry]] through her work on [[biomolecule|biomolecular materials]], DNA-protein interactions, and the applications of [[Atomic Force Microscopy]] to biological materials.


==Education==
==Education==
Hansma earned her Bachelor's degree in Chemistry from [[Earlham College]] in 1967, researching zinc-azine coordination compounds with William Stratton. Then she obtained a Master's degree in Biochemistry at the [[University of California, Berkeley]], under the supervision of H. A. Barker. Her 1969 thesis was titled "Separation of Basic Amino Acids and Resolution of D and L Isomers by Gas Liquid [[Chromatography]]." She then did research in the UC Berkeley Nutrition Department on cholesterol-fed guinea pigs in the lab of Rosemarie Ostwald.<ref>{{cite web|url=https://pdf.sciencedirectassets.com/778418/1-s2.0-S0022227520X64248/1-s2.0-S0022227520393408/main.pdf?X-Amz-Security-Token=IQoJb3JpZ2luX2VjEI7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaCXVzLWVhc3QtMSJHMEUCIQDx0DPIn9X2bR%2BpnmSsesJ6YQAcdLJXNJBI8JAYra2tFwIgNBlw2GsYPUjN1YRIJzJ9sJAx4NKbmudS%2FuvrpO%2FrRI0qswUIJxAFGgwwNTkwMDM1NDY4NjUiDHcoqgkxf6A8PE%2BjaiqQBWK09zNxAeP3enivi1B1GeohOlKcfDZ%2FdrXnld8hCwTfO7hMbZ2Jl3HuAqnI77EG%2B2jcuWJRhoHBWLlYUFngIQsGzC03SZB%2F9IuBfCvqp8xGl3Tesv42UNaFyb8ZLauHLDMA6kDV7sDU1EPfq%2F3tPaFkhtk90I2JlnkvajLLtH4mT%2FueJUUzG7TqhBsb1JUjs615HNuL82WE4wgl7XsjZs1dGS4pDpDYa7CgHm7k6mzZkQ7sTS%2FDmlvera1uWpjlbtsnuhzwAEiYEJUahO%2BPKeG7lMfgRKzOm%2F%2BZj%2FW%2Fivx4zxaRAivI638wK2MiEm1YbSirF%2BbVsC%2FHIAcotpQ%2FkEpIxz7LbcUwACFqWXrUAdNoHlA8StfePPRDbO94EP9rFjvNDL4S6wbt63GKPUbB6tx2BrPxCgydIFPSkPpseCxFx4FMTyqDROgmVhnX5wRgouNEqxS%2BA7n6p4h%2B8wLlMMXcLl0%2FTg%2Bc5bfrrGm3LOJmjdUMaZSZhLgOJCn%2FTyuBzB%2F0Hb%2FF1lwUXTKUdp5E649z1%2B%2FFzpZXJYWY79QnzxmZsGnwp237B%2B%2FvGjRn0MJ64AWfLSOYfq35nOamSOpBZ32EKcSjC809ReV6zoetp%2FBDytp%2B%2FaTHe902PQrKuHbs8SyU1atgXUbluhI4Liqby70EKaiI9Wc%2Bd4GdhOG6FqwQTtKyRrSXq3%2FbwVFs78nEVRjVb3XaR9awPGZdunna0ZgU%2F5pjDyvpT81XZODQAxFow4DLqucT4FO1OzEGIT0rcBr2xxMUZf2uMl6zagqoeyxhiOjhk%2FrSTowsnVlzNdcJaU8pY2M0JMVeW%2BYGouWYqMM62Fw8eYTGgqiCID6AZFVyHLZYLejNDmNLKowp1AQEMIDF%2FaUGOrEBRnghrC2i2b4axk7J%2BWvsOBnHfP2gdoi6XRjVwP%2BGrMU9Z%2B20k4s9XOA86e3%2Fm3U9Hb7VKDrAFiMPxP%2FjqvZtUBqJ8Pv%2F6XvbXPGN2fWCZBsVCvDC81ccbztPcl5rD%2BTz51Z5TkYvI7%2BHnoRb6%2B8%2FUAR5LcQYJiABF%2FRCjOlhsKzdp6bIONV3VWbU1fCuJfnuK65B8zgRtr2LDaCvtqcbC6fQoNP1sesop8%2F3unwTB%2B7l&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20230725T063045Z&X-Amz-SignedHeaders=host&X-Amz-Expires=300&X-Amz-Credential=ASIAQ3PHCVTY6RROWC65%2F20230725%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=f8195a3fee3fe6afcc2342809e2198d26823512fb59f6fa2c001ebb444742d4d&hash=6367e16773606ff242e8af0577efc4fcccb7d1a5982dc4bdcaa6e6f606a0733d&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=S0022227520393408&tid=spdf-90702acd-19a4-458b-8f3d-7b5c20cecfa3&sid=a9ecc25a244e824ffb6a8ae89a5a4e4331b2gxrqb&type=client&tsoh=d3d3LnNjaWVuY2VkaXJlY3QuY29t&ua=150d520a075054075356&rr=7ec25b24384e4d63&cc=pk|title=Effects of plasma lipoproteins from control and cholesterol-fed guinea pigs on red cell morphology and cholesterol content: an in vitro study}}</ref> In 1972, she enrolled in the PhD program in Biological Sciences at the University of California, Santa Barbara, where she studied behavioral mutants of [[Paramecium aurelia]]. Her research explored ion fluxes and ciliary membrane proteins in the lab of Ching Kung. Her thesis was titled "Biochemical Studies on the Behavioral Mutants of Paramecium aurelia: Ion Fluxes and Ciliary Membrane Proteins".<ref>{{cite web|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1550-7408.1975.tb05861.x|title=The Immobilization Antigen of Paramecium aurelia is a Single Polypeptide Chain}}</ref>
Hansma earned her Bachelor's degree in Chemistry from [[Earlham College]] in 1967, researching zinc-azine coordination compounds with William Stratton. Then she obtained a Master's degree in Biochemistry at the [[University of California, Berkeley]], under the supervision of H. A. Barker. Her 1969 thesis was titled "Separation of Basic Amino Acids and Resolution of D and L Isomers by Gas Liquid [[Chromatography]]." She then did research in the UC Berkeley Nutrition Department on cholesterol-fed guinea pigs in the lab of Rosemarie Ostwald.<ref>{{Cite web|url=https://www.sciencedirect.com/?ref=pdf_download&fr=RR-11&rr=7ec271832a6e07c4|title=ScienceDirect.com &#124; Science, health and medical journals, full text articles and books.|website=www.sciencedirect.com}}</ref> In 1972, she enrolled in the PhD program in Biological Sciences at the University of California, Santa Barbara, where she studied behavioral mutants of [[Paramecium aurelia]]. Her research explored ion fluxes and ciliary membrane proteins in the lab of Ching Kung. Her thesis was titled "Biochemical Studies on the Behavioral Mutants of Paramecium aurelia: Ion Fluxes and Ciliary Membrane Proteins".<ref>{{Cite journal|url=https://onlinelibrary.wiley.com/doi/10.1111/j.1550-7408.1975.tb05861.x|title=The Immobilization Antigen of Paramecium aurelia is a Single Polypeptide Chain|first=Helen G.|last=Hansma|date=May 25, 1975|journal=The Journal of Protozoology|volume=22|issue=2|pages=257–259|via=CrossRef|doi=10.1111/j.1550-7408.1975.tb05861.x}}</ref>


==Career==
==Career==
In 1977, Hansma started her academic career as an Assistant Research Biologist at the University of California, Santa Barbara, where she worked as the Principal Investigator of "The Molecular Mechanism of Membrane Excitation in Paramecium". She then held appointments as Science Consultant at Isla Vista School from 1981 to 1988 and at the University of California, Santa Barbara, starting in 1987 as an Assistant Research Biochemist in the Department of Physics. She was promoted to Associate Research Biochemist in 1993. In addition to her research appointments, she also served as an Adjunct Associate Professor at [[UCSB College of Engineering|UCSB]] from 1998 to 2004. From 2004 to 2008 she was a Program Manager at the [[National Science Foundation|NSF]] Directorate for Biological Sciences–Division of Biological Infrastructure (BIO-DBI).<ref>{{cite web|url=https://slideplayer.com/slide/14319249/|title=Funding Opportunities at the National Science Foundation - ppt download }}</ref> Since 2008, she has held the positions of Researcher Emeritus and Associate Adjunct Professor Emeritus at the University of California, Santa Barbara.<ref>{{cite web|url=https://www.news.ucsb.edu/2022/020714/life-imitates-mica|title= Life Imitates Mica -The Current}}</ref>
In 1977, Hansma started her academic career as an Assistant Research Biologist at the University of California, Santa Barbara, where she worked as the Principal Investigator of "The Molecular Mechanism of Membrane Excitation in Paramecium". She then held appointments as Science Consultant at Isla Vista School from 1981 to 1988 and at the University of California, Santa Barbara, starting in 1987 as an Assistant Research Biochemist in the Department of Physics. She was promoted to Associate Research Biochemist in 1993. In addition to her research appointments, she also served as an Adjunct Associate Professor at [[UCSB College of Engineering|UCSB]] from 1998 to 2004. From 2004 to 2008 she was a Program Manager at the [[National Science Foundation|NSF]] Directorate for Biological Sciences–Division of Biological Infrastructure (BIO-DBI).<ref>{{Cite web|url=https://slideplayer.com/slide/14319249/|title=Funding Opportunities at the National Science Foundation - ppt download|first=James Rodman, Mark Courtney, Sam Scheiner, Carter Kimsey, Rita Teutonico, Alan Tessier atessier, Sally O’Connor soconnor|last=Grant|website=slideplayer.com}}</ref> Since 2008, she has held the positions of Researcher Emeritus and Associate Adjunct Professor Emeritus at the University of California, Santa Barbara.<ref>{{Cite web|url=https://www.news.ucsb.edu/2022/020714/life-imitates-mica|title=Life Imitates Mica|date=September 20, 2022|website=The Current}}</ref>


==Research==
==Research==
Hansma’s research interests span the fields of biophysics and biochemistry. Working with Paul Hansma in the Physics Department, she applied Atomic Force Microscopy (AFM) to studying biomolecules. She was the Principal Investigator of NSF grants from 1991-1994,<ref>{{cite web|url=https://www.nsf.gov/awardsearch/showAward?AWD_ID=9018846&HistoricalAwards=false|title=Sequencing DNA with the Atomic Force Microscope}}</ref> 1994-1997, 1997-2000 and 2000-2003.<ref>{{cite web|url=https://www.nsf.gov/awardsearch/showAward?AWD_ID=9982743|title=New Applications for Scanning Probe Microscopy of Biomaterials}}</ref> She has conducted research on imaging and manipulating molecules on mica surfaces using AFM.<ref>{{cite web|url=https://scholar.google.com/citations?user=_4jz5LkAAAAJ&hl=en|title= Helen Greenwood Hansma - Google Scholar }}</ref> Since 2007, her major area of research is the origin of life. She hypothesizes that life originated between [[mica]] sheets and that the [[mechanical energy]] of mica sheets, moving apart and together, might have provided energy before chemical energy was available.<ref>{{cite web|url=https://www.scipod.global/dr-helen-greenwood-hansma-energy-a-clue-to-the-origins-of-life/|title= Dr Helen Greenwood Hansma - Energy: A Clue to the Origins of Life • scipod.global }}</ref>
Hansma’s research interests span the fields of biophysics and biochemistry. Working with Paul Hansma in the Physics Department, she applied Atomic Force Microscopy (AFM) to studying biomolecules. She was the Principal Investigator of NSF grants from 1991-1994,<ref>{{Cite web|url=https://www.nsf.gov/awardsearch/showAward?AWD_ID=9018846&HistoricalAwards=false|title=NSF Award Search: Award # 9018846 - Sequencing DNA with the Atomic Force Microscope|website=www.nsf.gov}}</ref> 1994-1997, 1997-2000 and 2000-2003.<ref>{{Cite web|url=https://www.nsf.gov/awardsearch/showAward?AWD_ID=9982743|title=NSF Award Search: Award # 9982743 - New Applications for Scanning Probe Microscopy of Biomaterials|website=www.nsf.gov}}</ref> She has conducted research on imaging and manipulating molecules on mica surfaces using AFM.<ref>{{Cite web|url=https://scholar.google.com/citations?user=_4jz5LkAAAAJ&hl=en|title=Helen Greenwood Hansma - Google Scholar}}</ref> Since 2007, her major area of research is the origin of life. She hypothesizes that life originated between [[mica]] sheets and that the [[mechanical energy]] of mica sheets, moving apart and together, might have provided energy before chemical energy was available.<ref>{{cite web|url=https://www.scipod.global/dr-helen-greenwood-hansma-energy-a-clue-to-the-origins-of-life/|title= Dr Helen Greenwood Hansma - Energy: A Clue to the Origins of Life • scipod.global }}</ref>


===Atomic force microscopy (AFM) of DNA and lipids ===
===Atomic force microscopy (AFM) of DNA and lipids ===
Hansma has worked on the applying AFM of DNA to illustrate its structure,<ref>{{cite web|url=https://academic.oup.com/nar/article-abstract/20/14/3585/2387323|title=Atomic force microscopy of single-and double-stranded DNA - Nucleic Acids Research - Oxford Academic}}</ref> its surface biology,<ref>{{cite web|url=https://www.annualreviews.org/doi/abs/10.1146/annurev.physchem.52.1.71|title=Surface Biology of DNA by Atomic Force Microscopy}}</ref> its motion,<ref>{{cite web|url=https://www.sciencedirect.com/science/article/pii/S0006349594807337|title=Research Article Motion and enzymatic degradation of DNA in the atomic force microscope}}</ref> and its condensation.<ref>{{cite web|url=https://academic.oup.com/nar/article/26/10/2481/1034344|title=DNA condensation for gene therapy as monitored by atomic force microscopy - Nucleic Acids Research -Oxford Academic}}</ref><ref>{{cite web|url=https://pubs.acs.org/doi/abs/10.1021/bi990901o|title=DNA Toroids: Stages in Condensation - Biochemistry}}</ref> She described advances in AFM of DNA<ref>{{cite web|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/sca.4950150509|title=Recent advances in atomic force microscopy of DNA - Hansma - 1993 - Scanning - Wiley Online Library}}</ref> and the benefits of using an aqueous solution for the imaging of DNA with AFM.<ref>{{cite web|url=https://academic.oup.com/nar/article-abstract/21/3/505/2386363|title=Atomic force microscopy of DNA in aqueous solutions - Nucleic Acids Research - Oxford Academic}}</ref> She then investigated the adsorption of DNA to various substrates using AFM and showed that the presence of a divalent cation greatly improves DNA adsorption, which requires electrostatic adsorption to the surface.<ref>{{cite web|url=https://pubs.acs.org/doi/pdf/10.1021/la00002a050|title=Adsorption of DNA to Mica, Silylated Mica, and Minerals: Characterization by Atomic Force Microscopy}}</ref> In related research, she used AFM to image small fragments of DNA that have been labeled with a chimeric protein fusion between streptavidin and two immunoglobulin G-binding domains of staphylococcal protein A.<ref>{{cite web|url=https://www.pnas.org/doi/abs/10.1073/pnas.90.9.3811|title=Atomic force microscopy of biochemically tagged DNA.}}</ref> While analyzing the efficacy of different modes of AFM she highlighted that the resolution is best in propanol while tapping AFM in dry helium provides a convenient way of imaging conformations of DNA molecules and positions of proteins on DNA. In an aqueous buffer, DNA molecules as small as 300 bp have been imaged even when in motion.<ref>{{cite web|url=https://www.sciencedirect.com/science/article/pii/S0006349595803437|title=Research Article Applications for atomic force microscopy of DNA}}</ref> She found that the binding of DNA to mica is correlated with the radius of the transition metal cation.<ref>{{cite web|url=https://www.sciencedirect.com/science/article/pii/S0006349596797576|title=Research Article DNA binding to mica correlates with cationic radius: assay by atomic force microscopy}}</ref>
Hansma has worked on the applying AFM of DNA to illustrate its structure,<ref>{{cite web|url=https://academic.oup.com/nar/article-abstract/20/14/3585/2387323|title=Atomic force microscopy of single-and double-stranded DNA - Nucleic Acids Research - Oxford Academic}}</ref> its surface biology,<ref>{{Cite journal|url=https://www.annualreviews.org/doi/10.1146/annurev.physchem.52.1.71|title=S URFACE B IOLOGY OF DNA BY A TOMIC F ORCE M ICROSCOPY|first=Helen G|last=Hansma|date=October 25, 2001|journal=Annual Review of Physical Chemistry|volume=52|issue=1|pages=71–92|via=CrossRef|doi=10.1146/annurev.physchem.52.1.71}}</ref> its motion,<ref>{{Cite journal|url=https://www.sciencedirect.com/science/article/pii/S0006349594807337|title=Motion and enzymatic degradation of DNA in the atomic force microscope|first1=M.|last1=Bezanilla|first2=B.|last2=Drake|first3=E.|last3=Nudler|first4=M.|last4=Kashlev|first5=P. K.|last5=Hansma|first6=H. G.|last6=Hansma|date=December 1, 1994|journal=Biophysical Journal|volume=67|issue=6|pages=2454–2459|via=ScienceDirect|doi=10.1016/S0006-3495(94)80733-7}}</ref> and its condensation.<ref>{{cite web|url=https://academic.oup.com/nar/article/26/10/2481/1034344|title=DNA condensation for gene therapy as monitored by atomic force microscopy - Nucleic Acids Research -Oxford Academic}}</ref><ref>{{Cite journal|url=https://pubs.acs.org/doi/10.1021/bi990901o|title=DNA Toroids: Stages in Condensation|first1=Roxana|last1=Golan|first2=Lía I.|last2=Pietrasanta|first3=Wan|last3=Hsieh|first4=Helen G.|last4=Hansma|date=October 1, 1999|journal=Biochemistry|volume=38|issue=42|pages=14069–14076|via=CrossRef|doi=10.1021/bi990901o}}</ref> She described advances in AFM of DNA<ref>{{Cite journal|url=https://onlinelibrary.wiley.com/doi/10.1002/sca.4950150509|title=Recent advances in atomic force microscopy of DNA: Recent advances in AFM of DNA|first1=Helen G.|last1=Hansma|first2=Robert L.|last2=Sinsheimer|first3=Jay|last3=Groppe|first4=Thomas C.|last4=Bruice|first5=Virgil|last5=Elings|first6=Gus|last6=Gurley|first7=Magdalena|last7=Bezanilla|first8=Iris A.|last8=Mastrangelo|first9=Paul V. C.|last9=Hough|first10=Paul K.|last10=Hansma|date=July 25, 1993|journal=Scanning|volume=15|issue=5|pages=296–299|via=CrossRef|doi=10.1002/sca.4950150509}}</ref> and the benefits of using an aqueous solution for the imaging of DNA with AFM.<ref>{{cite web|url=https://academic.oup.com/nar/article-abstract/21/3/505/2386363|title=Atomic force microscopy of DNA in aqueous solutions - Nucleic Acids Research - Oxford Academic}}</ref> She then investigated the adsorption of DNA to various substrates using AFM and showed that the presence of a divalent cation greatly improves DNA adsorption, which requires electrostatic adsorption to the surface.<ref>{{Cite journal|url=https://pubs.acs.org/doi/abs/10.1021/la00002a050|title=Adsorption of DNA to Mica, Silylated Mica, and Minerals: Characterization by Atomic Force Microscopy|first1=Magdalena|last1=Bezanilla|first2=Srinivas|last2=Manne|first3=Daniel E.|last3=Laney|first4=Yuri L.|last4=Lyubchenko|first5=Helen G.|last5=Hansma|date=February 25, 1995|journal=Langmuir|volume=11|issue=2|pages=655–659|via=CrossRef|doi=10.1021/la00002a050}}</ref> In related research, she used AFM to image small fragments of DNA that have been labeled with a chimeric protein fusion between streptavidin and two immunoglobulin G-binding domains of staphylococcal protein A.<ref>{{Cite journal|url=https://pnas.org/doi/full/10.1073/pnas.90.9.3811|title=Atomic force microscopy of biochemically tagged DNA.|first1=M N|last1=Murray|first2=H G|last2=Hansma|first3=M|last3=Bezanilla|first4=T|last4=Sano|first5=D F|last5=Ogletree|first6=W|last6=Kolbe|first7=C L|last7=Smith|first8=C R|last8=Cantor|first9=S|last9=Spengler|first10=P K|last10=Hansma|date=May 25, 1993|journal=Proceedings of the National Academy of Sciences|volume=90|issue=9|pages=3811–3814|via=CrossRef|doi=10.1073/pnas.90.9.3811|pmid=8483898|pmc=PMC46395}}</ref> While analyzing the efficacy of different modes of AFM she highlighted that the resolution is best in propanol while tapping AFM in dry helium provides a convenient way of imaging conformations of DNA molecules and positions of proteins on DNA. In an aqueous buffer, DNA molecules as small as 300 bp have been imaged even when in motion.<ref>{{Cite journal|url=https://www.sciencedirect.com/science/article/pii/S0006349595803437|title=Applications for atomic force microscopy of DNA|first1=H. G.|last1=Hansma|first2=D. E.|last2=Laney|first3=M.|last3=Bezanilla|first4=R. L.|last4=Sinsheimer|first5=P. K.|last5=Hansma|date=May 1, 1995|journal=Biophysical Journal|volume=68|issue=5|pages=1672–1677|via=ScienceDirect|doi=10.1016/S0006-3495(95)80343-7}}</ref> She found that the binding of DNA to mica is correlated with the radius of the transition metal cation.<ref>{{Cite journal|url=https://www.sciencedirect.com/science/article/pii/S0006349596797576|title=DNA binding to mica correlates with cationic radius: assay by atomic force microscopy|first1=H. G.|last1=Hansma|first2=D. E.|last2=Laney|date=April 1, 1996|journal=Biophysical Journal|volume=70|issue=4|pages=1933–1939|via=ScienceDirect|doi=10.1016/S0006-3495(96)79757-6}}</ref>


Hansma also examined the potential applications of atomic force microscopy (AFM) of DNA to the human genome project and stated that the AFM is capable of imaging DNA reproducibly but is not capable of sequencing DNA without further improvements.<ref>{{cite web|url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/1891/0000/Potential-applications-of-atomic-force-microscopy-of-DNA-to-the/10.1117/12.146705.full?SSO=1|title=Potential applications of atomic force microscopy of DNA to the human genome project}}</ref> Additionally, she has worked on the AFM of lipids and showed its usefulness in imaging biological processes.<ref>{{cite web|url=https://academic.oup.com/clinchem/article-abstract/37/9/1497/5649604|title=Atomic force microscopy: seeing molecules of lipid and immunoglobulin }}</ref> She has also studied lipid membranes and showed that AFM was capable of visualizing the defects in the lipid bilayers.<ref>{{cite web|url=https://pubs.aip.org/aip/acp/article/241/1/144/603655/Morphology-of-Polymerized-Membranes-on-an|title=Morphology of Polymerized Membranes on an Amorphous Substrate at Molecular Resolution by AFM}}</ref>
Hansma also examined the potential applications of atomic force microscopy (AFM) of DNA to the human genome project and stated that the AFM is capable of imaging DNA reproducibly but is not capable of sequencing DNA without further improvements.<ref>{{Cite web|url=https://www.spiedigitallibrary.org/conference-proceedings-of-spie/1891/0000/Potential-applications-of-atomic-force-microscopy-of-DNA-to-the/10.1117/12.146705.full|title=Potential applications of atomic force microscopy of DNA to the human genome project|first1=Helen G.|last1=Hansma|first2=Paul K.|last2=Hansma|date=June 24, 1993|publisher=SPIE|volume=1891|pages=66–70|via=www.spiedigitallibrary.org|doi=10.1117/12.146705}}</ref> Additionally, she has worked on the AFM of lipids and showed its usefulness in imaging biological processes.<ref>{{cite web|url=https://academic.oup.com/clinchem/article-abstract/37/9/1497/5649604|title=Atomic force microscopy: seeing molecules of lipid and immunoglobulin }}</ref> She has also studied lipid membranes and showed that AFM was capable of visualizing the defects in the lipid bilayers.<ref>{{cite web|url=https://pubs.aip.org/aip/acp/article/241/1/144/603655/Morphology-of-Polymerized-Membranes-on-an|title=Morphology of Polymerized Membranes on an Amorphous Substrate at Molecular Resolution by AFM}}</ref>


===Atomic force microscopy of spider silks and bacterial biofilms===
===Atomic force microscopy of spider silks and bacterial biofilms===
Near the turn of the millennium, Hansma’s research included the AFM of spider silks<ref>{{cite web|url=https://link.springer.com/chapter/10.1007/978-94-007-7119-2_7|title=tomic Force Microscopy and Spectroscopy of Silk from Spider Draglines, Capture-Web Spirals, and Silkworms}}</ref> and bacterial biofilms. She evaluated the use of atomic force microscopy and single-molecule force spectroscopy to study the structure of spider dragline silk<ref>{{cite web|url=https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/abs/nanofiber-formation-in-spider-draglinesilk-as-probed-by-atomic-force-microscopy-and-molecular-pulling/44E875FEE9FD4AD6897AA7C1E1D30493|title=Nanofiber Formation in Spider Dragline-Silk as Probed by Atomic Force Microscopy and Molecular Pulling - MRS Online Proceedings Library (OPL)}}</ref> and demonstrated its modular sacrificial bonds that contribute to its strength and toughness.<ref>{{cite web|url=https://www.nature.com/articles/nmat858|title=Molecular nanosprings in spider capture-silk threads - Nature Materials}}</ref> Using an artificial silk protein provided by researchers from the U.S. Army Natick R&D Center, she then presented models for molecular and supramolecular structures of the protein, derived from amino acid sequences, force spectroscopy, and stretching of bulk capture web.<ref>{{cite web|url=https://www.pnas.org/doi/abs/10.1073/pnas.082526499|title=Segmented nanofibers of spider dragline silk: Atomic force microscopy and single-molecule force spectroscopy}}</ref> Furthermore, with Patricia Holden and members of her lab, she analyzed the surface properties and physical morphology of Pseudomonas putida biofilms<ref>{{cite web|url=https://journals.asm.org/doi/full/10.1128/JB.182.13.3809-3815.2000|title=Physical Morphology and Surface Properties of Unsaturated Pseudomonas putida Biofilms - Journal of Bacteriology}}</ref> and investigated how biofilm bacteria adapt to low nutrient availability in unsaturated environments.<ref>{{cite web|url=https://www.jstor.org/stable/4287616|title=Elongation Correlates with Nutrient Deprivation in Pseudomonas aeruginosa-Unsaturated Biofilms }}</ref>
Near the turn of the millennium, Hansma’s research included the AFM of spider silks<ref>{{Cite book|url=https://doi.org/10.1007/978-94-007-7119-2_7|title=Biotechnology of Silk|first=Helen Greenwood|last=Hansma|editor-first1=Tetsuo|editor-last1=Asakura|editor-first2=Thomas|editor-last2=Miller|date=July 25, 2014|publisher=Springer Netherlands|pages=123–136|via=Springer Link|doi=10.1007/978-94-007-7119-2_7}}</ref> and bacterial biofilms. She evaluated the use of atomic force microscopy and single-molecule force spectroscopy to study the structure of spider dragline silk<ref>{{Cite journal|url=https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/abs/nanofiber-formation-in-spider-draglinesilk-as-probed-by-atomic-force-microscopy-and-molecular-pulling/44E875FEE9FD4AD6897AA7C1E1D30493|title=Nanofiber Formation in Spider Dragline-Silk as Probed by Atomic Force Microscopy and Molecular Pulling|first1=Emin|last1=Oroudjev|first2=Cheryl Y.|last2=Hayashi|first3=Jason|last3=Soares|first4=Steven|last4=Arcidiacono|first5=Stephen A.|last5=Fossey|first6=Helen G.|last6=Hansma|date=January 25, 2002|journal=MRS Online Proceedings Library (OPL)|volume=738|pages=G10.4|via=Cambridge University Press|doi=10.1557/PROC-738-G10.4}}</ref> and demonstrated its modular sacrificial bonds that contribute to its strength and toughness.<ref>{{Cite journal|url=https://www.nature.com/articles/nmat858|title=Molecular nanosprings in spider capture-silk threads|first1=Nathan|last1=Becker|first2=Emin|last2=Oroudjev|first3=Stephanie|last3=Mutz|first4=Jason P.|last4=Cleveland|first5=Paul K.|last5=Hansma|first6=Cheryl Y.|last6=Hayashi|first7=Dmitrii E.|last7=Makarov|first8=Helen G.|last8=Hansma|date=April 25, 2003|journal=Nature Materials|volume=2|issue=4|pages=278–283|via=www.nature.com|doi=10.1038/nmat858}}</ref> Using an artificial silk protein provided by researchers from the U.S. Army Natick R&D Center, she then presented models for molecular and supramolecular structures of the protein, derived from amino acid sequences, force spectroscopy, and stretching of bulk capture web.<ref>{{Cite journal|url=https://pnas.org/doi/full/10.1073/pnas.082526499|title=Segmented nanofibers of spider dragline silk: Atomic force microscopy and single-molecule force spectroscopy|first1=E.|last1=Oroudjev|first2=J.|last2=Soares|first3=S.|last3=Arcidiacono|first4=J. B.|last4=Thompson|first5=S. A.|last5=Fossey|first6=H. G.|last6=Hansma|date=April 30, 2002|journal=Proceedings of the National Academy of Sciences|volume=99|issue=suppl_2|pages=6460–6465|via=CrossRef|doi=10.1073/pnas.082526499|pmid=11959907|pmc=PMC128550}}</ref> Furthermore, with Patricia Holden and members of her lab, she analyzed the surface properties and physical morphology of Pseudomonas putida biofilms<ref>{{Cite journal|url=https://journals.asm.org/doi/10.1128/JB.182.13.3809-3815.2000|title=Physical Morphology and Surface Properties of Unsaturated Pseudomonas putida Biofilms|first1=Ilene D.|last1=Auerbach|first2=Cody|last2=Sorensen|first3=Helen G.|last3=Hansma|first4=Patricia A.|last4=Holden|date=July 25, 2000|journal=Journal of Bacteriology|volume=182|issue=13|pages=3809–3815|via=CrossRef|doi=10.1128/JB.182.13.3809-3815.2000|pmid=10850998|pmc=PMC94554}}</ref> and investigated how biofilm bacteria adapt to low nutrient availability in unsaturated environments.<ref>{{Cite web|url=http://www.jstor.org/stable/4287616|title=Elongation Correlates with Nutrient Deprivation in Pseudomonas aeruginosa-Unsaturated Biofilms|author1=R. E. Steinberger|author2=Allen, A. R.|author3=Hansma, H. G.|author4=P. A. Holden|year=2002|journal=Microbial Ecology|volume=43|issue=4|pages=416-423|via=JSTOR}}</ref>


===Origin of life and mica sheets===
===Origin of life and mica sheets===
Hansma is also known for her work on mica sheets and the origin of life.<ref>{{cite web|url=https://academic.oup.com/mt/article/18/6/16/6820774|title=Atomic Force Microscopy of Biomaterials, Mica, and the Origins of Life}}</ref> In her paper, "Possible origin of life between mica sheets: does life imitate mica?" she explored various elements that support her hypothesis regarding the origin of life between mica sheets. She noted that these sheets provide stable compartments, mechanical energy for bond formation, and isolation needed for Darwinian evolution. Moving mica sheets have the ability to facilitate mechanochemistry, resulting in the synthesis of prebiotic organic molecules.<ref>{{cite web|url=https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/abs/could-life-originate-between-mica-sheets-mechanochemical-biomolecular-synthesis-and-the-origins-of-life/E5433CA1FBE917AEB84C7EA078E7321C|title=Could Life Originate between Mica Sheets?: Mechanochemical Biomolecular Synthesis and the Origins of Life}}</ref> She highlighted key resemblances between life and the hypothetical origin between mica sheets.<ref>{{cite web|url=https://www.tandfonline.com/doi/full/10.1080/07391102.2012.718528|title=Full article: Possible origin of life between mica sheets: does life imitate mica?}}</ref> In 2014, she suggested that the likelihood of life's emergence increases with an increase in molecular crowding, and the confined spaces between Muscovite mica sheets provide advantages for the origins of life.<ref>{{cite web|url=https://link.springer.com/article/10.1007/s11084-014-9382-5|title=The Power of Crowding for the Origins of Life}}</ref>
Hansma is also known for her work on mica sheets and the origin of life.<ref>{{cite web|url=https://academic.oup.com/mt/article/18/6/16/6820774|title=Atomic Force Microscopy of Biomaterials, Mica, and the Origins of Life}}</ref> In her paper, "Possible origin of life between mica sheets: does life imitate mica?" she explored various elements that support her hypothesis regarding the origin of life between mica sheets. She noted that these sheets provide stable compartments, mechanical energy for bond formation, and isolation needed for Darwinian evolution. Moving mica sheets have the ability to facilitate mechanochemistry, resulting in the synthesis of prebiotic organic molecules.<ref>{{Cite journal|url=https://www.cambridge.org/core/journals/mrs-online-proceedings-library-archive/article/abs/could-life-originate-between-mica-sheets-mechanochemical-biomolecular-synthesis-and-the-origins-of-life/E5433CA1FBE917AEB84C7EA078E7321C|title=Could Life Originate between Mica Sheets?: Mechanochemical Biomolecular Synthesis and the Origins of Life|first=Helen Greenwood|last=Hansma|date=January 25, 2009|journal=MRS Online Proceedings Library (OPL)|volume=1185|pages=1185|via=Cambridge University Press|doi=10.1557/PROC-1185-II03-15}}</ref> She highlighted key resemblances between life and the hypothetical origin between mica sheets.<ref>{{Cite journal|url=http://www.tandfonline.com/doi/abs/10.1080/07391102.2012.718528|title=Possible origin of life between mica sheets: does life imitate mica?|first=Helen Greenwood|last=Hansma|date=August 25, 2013|journal=Journal of Biomolecular Structure and Dynamics|volume=31|issue=8|pages=888–895|via=CrossRef|doi=10.1080/07391102.2012.718528|pmid=22963072|pmc=PMC3725661}}</ref> In 2014, she suggested that the likelihood of life's emergence increases with an increase in molecular crowding, and the confined spaces between Muscovite mica sheets provide advantages for the origins of life.<ref>{{Cite journal|url=https://doi.org/10.1007/s11084-014-9382-5|title=The Power of Crowding for the Origins of Life|first=Helen Greenwood|last=Hansma|date=December 1, 2014|journal=Origins of Life and Evolution of Biospheres|volume=44|issue=4|pages=307–311|via=Springer Link|doi=10.1007/s11084-014-9382-5}}</ref>


Later, in 2017, Hansma proposed that membraneless organelles, or biomolecular condensates, may have existed prior to the emergence of membrane-bound structures during the origins of life. These biomolecular condensates typically contain RNA and protein and could have formed and sheltered in the interstitial spaces between mica sheets, which offer favorable conditions for the origin and development of life.<ref>{{cite web|url=https://www.mdpi.com/2075-1729/7/2/28|title=Better than Membranes at the Origin of Life?}}</ref> During her research on the origin of life, she discussed the prevalence of mechanical forces and mechanical energy in living cells and suggested that these may have preceded chemical energy at life's origins.<ref>{{cite web|url=https://www.mdpi.com/2413-4155/2/4/88|title=Mechanical Energy before Chemical Energy at the Origins of Life? }}</ref>
Later, in 2017, Hansma proposed that membraneless organelles, or biomolecular condensates, may have existed prior to the emergence of membrane-bound structures during the origins of life. These biomolecular condensates typically contain RNA and protein and could have formed and sheltered in the interstitial spaces between mica sheets, which offer favorable conditions for the origin and development of life.<ref>{{Cite journal|url=https://www.mdpi.com/2075-1729/7/2/28|title=Better than Membranes at the Origin of Life?|first=Helen Greenwood|last=Hansma|date=June 25, 2017|journal=Life|volume=7|issue=2|pages=28|via=www.mdpi.com|doi=10.3390/life7020028}}</ref> During her research on the origin of life, she discussed the prevalence of mechanical forces and mechanical energy in living cells and suggested that these may have preceded chemical energy at life's origins.<ref>{{Cite journal|url=https://www.mdpi.com/2413-4155/2/4/88|title=Mechanical Energy before Chemical Energy at the Origins of Life?|first=Helen Greenwood|last=Hansma|date=December 25, 2020|journal=Sci|volume=2|issue=4|pages=88|via=www.mdpi.com|doi=10.3390/sci2040088}}</ref>


==Selected articles==
==Selected articles==

Revision as of 06:46, 25 July 2023

Helen Greenwood Hansma
NationalityAmerican
Occupation(s)Biologist, biophysicist, biochemist, and academic
Academic background
EducationB.S. in Chemistry
M.S. in Biochemistry
PhD in Biological Sciences
Alma materEarlham College
University of California, Berkeley
University of California, Santa Barbara
ThesisBiochemical Studies on the Behavioral Mutants of Paramecium aurelia: Ion Fluxes and Ciliary Membrane Proteins (1974)
Doctoral advisorChing Kung
Academic work
InstitutionsUniversity of California, Santa Barbara
UCLA [post doc]

Helen Greenwood Hansma is an American biologist, biophysicist, biochemist, and academic. She is a Researcher Emeritus and Associate Adjunct Professor Emeritus at the University of California, Santa Barbara.[1]

Hansma’s research revolves around understanding the origin of life and proposes that life originated between mica sheets in micaceous clay.[2] She has contributed to the fields of biophysics and biochemistry through her work on biomolecular materials, DNA-protein interactions, and the applications of Atomic Force Microscopy to biological materials.

Education

Hansma earned her Bachelor's degree in Chemistry from Earlham College in 1967, researching zinc-azine coordination compounds with William Stratton. Then she obtained a Master's degree in Biochemistry at the University of California, Berkeley, under the supervision of H. A. Barker. Her 1969 thesis was titled "Separation of Basic Amino Acids and Resolution of D and L Isomers by Gas Liquid Chromatography." She then did research in the UC Berkeley Nutrition Department on cholesterol-fed guinea pigs in the lab of Rosemarie Ostwald.[3] In 1972, she enrolled in the PhD program in Biological Sciences at the University of California, Santa Barbara, where she studied behavioral mutants of Paramecium aurelia. Her research explored ion fluxes and ciliary membrane proteins in the lab of Ching Kung. Her thesis was titled "Biochemical Studies on the Behavioral Mutants of Paramecium aurelia: Ion Fluxes and Ciliary Membrane Proteins".[4]

Career

In 1977, Hansma started her academic career as an Assistant Research Biologist at the University of California, Santa Barbara, where she worked as the Principal Investigator of "The Molecular Mechanism of Membrane Excitation in Paramecium". She then held appointments as Science Consultant at Isla Vista School from 1981 to 1988 and at the University of California, Santa Barbara, starting in 1987 as an Assistant Research Biochemist in the Department of Physics. She was promoted to Associate Research Biochemist in 1993. In addition to her research appointments, she also served as an Adjunct Associate Professor at UCSB from 1998 to 2004. From 2004 to 2008 she was a Program Manager at the NSF Directorate for Biological Sciences–Division of Biological Infrastructure (BIO-DBI).[5] Since 2008, she has held the positions of Researcher Emeritus and Associate Adjunct Professor Emeritus at the University of California, Santa Barbara.[6]

Research

Hansma’s research interests span the fields of biophysics and biochemistry. Working with Paul Hansma in the Physics Department, she applied Atomic Force Microscopy (AFM) to studying biomolecules. She was the Principal Investigator of NSF grants from 1991-1994,[7] 1994-1997, 1997-2000 and 2000-2003.[8] She has conducted research on imaging and manipulating molecules on mica surfaces using AFM.[9] Since 2007, her major area of research is the origin of life. She hypothesizes that life originated between mica sheets and that the mechanical energy of mica sheets, moving apart and together, might have provided energy before chemical energy was available.[10]

Atomic force microscopy (AFM) of DNA and lipids

Hansma has worked on the applying AFM of DNA to illustrate its structure,[11] its surface biology,[12] its motion,[13] and its condensation.[14][15] She described advances in AFM of DNA[16] and the benefits of using an aqueous solution for the imaging of DNA with AFM.[17] She then investigated the adsorption of DNA to various substrates using AFM and showed that the presence of a divalent cation greatly improves DNA adsorption, which requires electrostatic adsorption to the surface.[18] In related research, she used AFM to image small fragments of DNA that have been labeled with a chimeric protein fusion between streptavidin and two immunoglobulin G-binding domains of staphylococcal protein A.[19] While analyzing the efficacy of different modes of AFM she highlighted that the resolution is best in propanol while tapping AFM in dry helium provides a convenient way of imaging conformations of DNA molecules and positions of proteins on DNA. In an aqueous buffer, DNA molecules as small as 300 bp have been imaged even when in motion.[20] She found that the binding of DNA to mica is correlated with the radius of the transition metal cation.[21]

Hansma also examined the potential applications of atomic force microscopy (AFM) of DNA to the human genome project and stated that the AFM is capable of imaging DNA reproducibly but is not capable of sequencing DNA without further improvements.[22] Additionally, she has worked on the AFM of lipids and showed its usefulness in imaging biological processes.[23] She has also studied lipid membranes and showed that AFM was capable of visualizing the defects in the lipid bilayers.[24]

Atomic force microscopy of spider silks and bacterial biofilms

Near the turn of the millennium, Hansma’s research included the AFM of spider silks[25] and bacterial biofilms. She evaluated the use of atomic force microscopy and single-molecule force spectroscopy to study the structure of spider dragline silk[26] and demonstrated its modular sacrificial bonds that contribute to its strength and toughness.[27] Using an artificial silk protein provided by researchers from the U.S. Army Natick R&D Center, she then presented models for molecular and supramolecular structures of the protein, derived from amino acid sequences, force spectroscopy, and stretching of bulk capture web.[28] Furthermore, with Patricia Holden and members of her lab, she analyzed the surface properties and physical morphology of Pseudomonas putida biofilms[29] and investigated how biofilm bacteria adapt to low nutrient availability in unsaturated environments.[30]

Origin of life and mica sheets

Hansma is also known for her work on mica sheets and the origin of life.[31] In her paper, "Possible origin of life between mica sheets: does life imitate mica?" she explored various elements that support her hypothesis regarding the origin of life between mica sheets. She noted that these sheets provide stable compartments, mechanical energy for bond formation, and isolation needed for Darwinian evolution. Moving mica sheets have the ability to facilitate mechanochemistry, resulting in the synthesis of prebiotic organic molecules.[32] She highlighted key resemblances between life and the hypothetical origin between mica sheets.[33] In 2014, she suggested that the likelihood of life's emergence increases with an increase in molecular crowding, and the confined spaces between Muscovite mica sheets provide advantages for the origins of life.[34]

Later, in 2017, Hansma proposed that membraneless organelles, or biomolecular condensates, may have existed prior to the emergence of membrane-bound structures during the origins of life. These biomolecular condensates typically contain RNA and protein and could have formed and sheltered in the interstitial spaces between mica sheets, which offer favorable conditions for the origin and development of life.[35] During her research on the origin of life, she discussed the prevalence of mechanical forces and mechanical energy in living cells and suggested that these may have preceded chemical energy at life's origins.[36]

Selected articles

  • Hansma, H. G., Vesenka, J., Siegerist, C., Kelderman, G., Morrett, H., Sinsheimer, R. L., ... & Hansma, P. K. (1992). Reproducible imaging and dissection of plasmid DNA under liquid with the atomic force microscope. Science, 256(5060), 1180-1184.
  • Hansma, H. G., & Hoh, J. H. (1994). Biomolecular imaging with the atomic force microscope. Annual review of biophysics and biomolecular structure, 23(1), 115-140.
  • Radmacher, M., Fritz, M., Hansma, H. G., & Hansma, P. K. (1994). Direct observation of enzyme activity with the atomic force microscope. Science, 265(5178), 1577-1579.
  • Hansma, H. G. (2001). Surface biology of DNA by atomic force microscopy. Annual Review of Physical Chemistry, 52(1), 71-92.
  • Hansma, H. G. (2017). Better than Membranes at the Origin of Life?. Life, 7(2), 28.
  • Hansma, H. G. (2022). DNA and the origins of life in micaceous clay. Biophysical Journal, 121(24), 4867-4873.
  • Hansma, H. G. (2023). Liquid–liquid phase separation at the origins of life. In Droplets of Life (pp. 251-268). Academic Press.

References

  1. ^ "AWIS Member Spotlight: Helen Greenwood Hansma, PhD". AWIS. January 18, 2023.
  2. ^ "DNA and the origins of life in micaceous clay: Biophysical Journal".
  3. ^ "ScienceDirect.com | Science, health and medical journals, full text articles and books". www.sciencedirect.com.
  4. ^ Hansma, Helen G. (May 25, 1975). "The Immobilization Antigen of Paramecium aurelia is a Single Polypeptide Chain". The Journal of Protozoology. 22 (2): 257–259. doi:10.1111/j.1550-7408.1975.tb05861.x – via CrossRef.
  5. ^ Grant, James Rodman, Mark Courtney, Sam Scheiner, Carter Kimsey, Rita Teutonico, Alan Tessier atessier, Sally O’Connor soconnor. "Funding Opportunities at the National Science Foundation - ppt download". slideplayer.com.{{cite web}}: CS1 maint: multiple names: authors list (link)
  6. ^ "Life Imitates Mica". The Current. September 20, 2022.
  7. ^ "NSF Award Search: Award # 9018846 - Sequencing DNA with the Atomic Force Microscope". www.nsf.gov.
  8. ^ "NSF Award Search: Award # 9982743 - New Applications for Scanning Probe Microscopy of Biomaterials". www.nsf.gov.
  9. ^ "Helen Greenwood Hansma - Google Scholar".
  10. ^ "Dr Helen Greenwood Hansma - Energy: A Clue to the Origins of Life • scipod.global".
  11. ^ "Atomic force microscopy of single-and double-stranded DNA - Nucleic Acids Research - Oxford Academic".
  12. ^ Hansma, Helen G (October 25, 2001). "S URFACE B IOLOGY OF DNA BY A TOMIC F ORCE M ICROSCOPY". Annual Review of Physical Chemistry. 52 (1): 71–92. doi:10.1146/annurev.physchem.52.1.71 – via CrossRef.
  13. ^ Bezanilla, M.; Drake, B.; Nudler, E.; Kashlev, M.; Hansma, P. K.; Hansma, H. G. (December 1, 1994). "Motion and enzymatic degradation of DNA in the atomic force microscope". Biophysical Journal. 67 (6): 2454–2459. doi:10.1016/S0006-3495(94)80733-7 – via ScienceDirect.
  14. ^ "DNA condensation for gene therapy as monitored by atomic force microscopy - Nucleic Acids Research -Oxford Academic".
  15. ^ Golan, Roxana; Pietrasanta, Lía I.; Hsieh, Wan; Hansma, Helen G. (October 1, 1999). "DNA Toroids: Stages in Condensation". Biochemistry. 38 (42): 14069–14076. doi:10.1021/bi990901o – via CrossRef.
  16. ^ Hansma, Helen G.; Sinsheimer, Robert L.; Groppe, Jay; Bruice, Thomas C.; Elings, Virgil; Gurley, Gus; Bezanilla, Magdalena; Mastrangelo, Iris A.; Hough, Paul V. C.; Hansma, Paul K. (July 25, 1993). "Recent advances in atomic force microscopy of DNA: Recent advances in AFM of DNA". Scanning. 15 (5): 296–299. doi:10.1002/sca.4950150509 – via CrossRef.
  17. ^ "Atomic force microscopy of DNA in aqueous solutions - Nucleic Acids Research - Oxford Academic".
  18. ^ Bezanilla, Magdalena; Manne, Srinivas; Laney, Daniel E.; Lyubchenko, Yuri L.; Hansma, Helen G. (February 25, 1995). "Adsorption of DNA to Mica, Silylated Mica, and Minerals: Characterization by Atomic Force Microscopy". Langmuir. 11 (2): 655–659. doi:10.1021/la00002a050 – via CrossRef.
  19. ^ Murray, M N; Hansma, H G; Bezanilla, M; Sano, T; Ogletree, D F; Kolbe, W; Smith, C L; Cantor, C R; Spengler, S; Hansma, P K (May 25, 1993). "Atomic force microscopy of biochemically tagged DNA". Proceedings of the National Academy of Sciences. 90 (9): 3811–3814. doi:10.1073/pnas.90.9.3811. PMC 46395. PMID 8483898 – via CrossRef.{{cite journal}}: CS1 maint: PMC format (link)
  20. ^ Hansma, H. G.; Laney, D. E.; Bezanilla, M.; Sinsheimer, R. L.; Hansma, P. K. (May 1, 1995). "Applications for atomic force microscopy of DNA". Biophysical Journal. 68 (5): 1672–1677. doi:10.1016/S0006-3495(95)80343-7 – via ScienceDirect.
  21. ^ Hansma, H. G.; Laney, D. E. (April 1, 1996). "DNA binding to mica correlates with cationic radius: assay by atomic force microscopy". Biophysical Journal. 70 (4): 1933–1939. doi:10.1016/S0006-3495(96)79757-6 – via ScienceDirect.
  22. ^ Hansma, Helen G.; Hansma, Paul K. (June 24, 1993). "Potential applications of atomic force microscopy of DNA to the human genome project". SPIE. pp. 66–70. doi:10.1117/12.146705 – via www.spiedigitallibrary.org.
  23. ^ "Atomic force microscopy: seeing molecules of lipid and immunoglobulin".
  24. ^ "Morphology of Polymerized Membranes on an Amorphous Substrate at Molecular Resolution by AFM".
  25. ^ Hansma, Helen Greenwood (July 25, 2014). Asakura, Tetsuo; Miller, Thomas (eds.). Biotechnology of Silk. Springer Netherlands. pp. 123–136. doi:10.1007/978-94-007-7119-2_7 – via Springer Link.
  26. ^ Oroudjev, Emin; Hayashi, Cheryl Y.; Soares, Jason; Arcidiacono, Steven; Fossey, Stephen A.; Hansma, Helen G. (January 25, 2002). "Nanofiber Formation in Spider Dragline-Silk as Probed by Atomic Force Microscopy and Molecular Pulling". MRS Online Proceedings Library (OPL). 738: G10.4. doi:10.1557/PROC-738-G10.4 – via Cambridge University Press.
  27. ^ Becker, Nathan; Oroudjev, Emin; Mutz, Stephanie; Cleveland, Jason P.; Hansma, Paul K.; Hayashi, Cheryl Y.; Makarov, Dmitrii E.; Hansma, Helen G. (April 25, 2003). "Molecular nanosprings in spider capture-silk threads". Nature Materials. 2 (4): 278–283. doi:10.1038/nmat858 – via www.nature.com.
  28. ^ Oroudjev, E.; Soares, J.; Arcidiacono, S.; Thompson, J. B.; Fossey, S. A.; Hansma, H. G. (April 30, 2002). "Segmented nanofibers of spider dragline silk: Atomic force microscopy and single-molecule force spectroscopy". Proceedings of the National Academy of Sciences. 99 (suppl_2): 6460–6465. doi:10.1073/pnas.082526499. PMC 128550. PMID 11959907 – via CrossRef.{{cite journal}}: CS1 maint: PMC format (link)
  29. ^ Auerbach, Ilene D.; Sorensen, Cody; Hansma, Helen G.; Holden, Patricia A. (July 25, 2000). "Physical Morphology and Surface Properties of Unsaturated Pseudomonas putida Biofilms". Journal of Bacteriology. 182 (13): 3809–3815. doi:10.1128/JB.182.13.3809-3815.2000. PMC 94554. PMID 10850998 – via CrossRef.{{cite journal}}: CS1 maint: PMC format (link)
  30. ^ R. E. Steinberger; Allen, A. R.; Hansma, H. G.; P. A. Holden (2002). "Elongation Correlates with Nutrient Deprivation in Pseudomonas aeruginosa-Unsaturated Biofilms". Microbial Ecology. pp. 416–423 – via JSTOR.
  31. ^ "Atomic Force Microscopy of Biomaterials, Mica, and the Origins of Life".
  32. ^ Hansma, Helen Greenwood (January 25, 2009). "Could Life Originate between Mica Sheets?: Mechanochemical Biomolecular Synthesis and the Origins of Life". MRS Online Proceedings Library (OPL). 1185: 1185. doi:10.1557/PROC-1185-II03-15 – via Cambridge University Press.
  33. ^ Hansma, Helen Greenwood (August 25, 2013). "Possible origin of life between mica sheets: does life imitate mica?". Journal of Biomolecular Structure and Dynamics. 31 (8): 888–895. doi:10.1080/07391102.2012.718528. PMC 3725661. PMID 22963072 – via CrossRef.{{cite journal}}: CS1 maint: PMC format (link)
  34. ^ Hansma, Helen Greenwood (December 1, 2014). "The Power of Crowding for the Origins of Life". Origins of Life and Evolution of Biospheres. 44 (4): 307–311. doi:10.1007/s11084-014-9382-5 – via Springer Link.
  35. ^ Hansma, Helen Greenwood (June 25, 2017). "Better than Membranes at the Origin of Life?". Life. 7 (2): 28. doi:10.3390/life7020028 – via www.mdpi.com.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  36. ^ Hansma, Helen Greenwood (December 25, 2020). "Mechanical Energy before Chemical Energy at the Origins of Life?". Sci. 2 (4): 88. doi:10.3390/sci2040088 – via www.mdpi.com.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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