Special issue for Klaus Gawrisch

What defines a highly respected scientist? There are many scientists who are outstanding in different aspects of our daily work, great mentors, great friends, great synthesizers, great reasoners, great experimentalists, great innovators, etc., but there is not a single formula. Nevertheless, when there is a groundswell of gratitude, concern, and an overwhelming sense of imminent loss among so very many biophysicists, we are certainly justified in paying a tribute to a scientist who preferred to consider himself just one expert among many. This special issue of Biophysical Journal arises out of exactly that scenario, and the huge energy of many of us was unambiguous in our determination to single out Klaus Gawrisch to honor for his many, many great attributes, including all of those above. Indeed, many of us have been depending on Klaus for his unsurpassed expertise on the nuclear magnetic resonance (NMR) of lipids and mixtures of lipids in membranes and the subtle but essential ways that lipid handling, the choice of solvents and detergents, and osmotic stress impact lipid and membrane protein hydration and configurations. "When stuck, call Klaus” has been excellent advice for many years. He has generously responded with long discussions replete with wisdom, data, and references, outlining with great mastery what should and should not be done. His authority is based on a lifetime of accumulating experimental data with his own hands on many different aspects of the chemical interactions of lipids and membrane proteins, as well as many interactions with collaborators with whom he widened his expertise. Son of a carpenter, Klaus was born in the last hours of 1950 in Freyburg, East Germany, where he trained as a mason in high school. This culminated in very high scores on the Abitur exams, resulting in Klaus being invited to study physics at Moscow State University (MSU), where he worked with N.N. Sergeyev on shift reagents in 13C NMR in the laboratory of biophysics led by Prof. Lev A. Blumenfeld. More importantly, Klaus met his wife Ludmila Archipowa, also an undergraduate at MSU in physics and the chief cook in the summer construction work program in the village of Chemodanovo (about 300 miles northeast of Moscow), where he was assigned. They married in 1972 and have two children and two grandchildren. After he earned his MS degree at MSU, Klaus and Ludmila moved to Leipzig, where Klaus worked in the physics department of Karl Marx University (the name for the University of Leipzig between 1951 and 1991). There, in the Laboratory of Molecular Physics, led by Prof. Dr. G. Klose, Klaus first studied with advisor Prof. Dr. K. Arnold on “31P and 2H NMR investigations of molecular motions in phospholipid water dispersions,” earning the Dr. rer. nat. (PhD) in 1979. In a second doctoral degree, Klaus studied the “molecular mechanisms of the polyethylene glycol induced cell fusion” with both Drs. Arnold and Klose, resulting in his doctor of science (Dr. sc. nat.) degree in 1986. By this point, Klaus had risen from assistant at the Laboratory of Molecular Physics to associate professor of biophysics at the Laboratory of Physics of Condensed Matter in the physics department, where he had become facultas docendi (University Lecturer) in 1985. Because of his outstanding work on each of these two subjects, Klaus was awarded the Leibniz Prize of the University of Leipzig in 1981 for education, training, and research and the best paper award at the 1985 International Scientific Conference on Membrane Organization for his work on the NMR of hydration forces. Dr. V. Adrian Parsegian attended this meeting, leading to Klaus’s invitation to join us in his laboratory at the NIH as a visiting fellow, the first one from the former Soviet Union in our experience. Despite a number of hardships, including waiting 2 years for permission to leave the GDR (granted only with retention in East Germany of Ludmila and their two children, Roland and Michael) and returning to a post-doc salary after achieving associate professor with tenure, Klaus readily accepted Parsegian’s invitation because “he wanted to be where the science was being made.” Luckily, the collapse of the Soviet Union allowed an opening of the borders about a year later, allowing Klaus to stay and for his family to ultimately join him. Despite his post-doc salary and the determination of Ludmila and Klaus to allow their children to complete their German education through the Abitur (private school), and Ludmila’s lack of a work visa, they managed to survive the high-cost locale of Bethesda, MD, USA, mainly through Ludmila’s expertise in cooking and sewing. This all changed when Klaus and Ludmila got their green cards, and Ludmila aced the Microsoft networking exams, allowing her to have a long-term job with the National Abortion Federation running their IT department, which she grew from two individuals on a phone line to a staff of 40, servicing the US, Canada, and Mexico with free information. Ludmila was simply shocked that here, in America, some men were making decisions about a woman’s body and that we were so far behind other nations, so she took the job despite the risks to herself and family. Indeed, she knew some of the murdered abortion providers, some killed in their churches. Klaus was soon able to start his own group by moving to another institute, first as a tenure track and then a senior investigator when he got tenure on January 15, 1998. His group, the Laboratory of Membrane Biochemistry and Biophysics, is still extant despite his retirement in 2020. The following paragraphs highlight some of Klaus’s work. From early on in his career, Klaus was contributing to the phase behavior of lipids in bilayers (1Arnold K. Gawrisch K. Scholl R. et al.NMR and calorimetric studies of thermal phase-transition of sonnicated aqueous dispersions of dipalmitoylphosphorylethanolamine and dihexadecylglycerolphosphatidic acid.Stud. Biophys. 1977; 64: 173-181Google Scholar,2Arnold K. Gawrisch K. Scholl R. et al.1H and 23Na NMR studies of thermal phase-transition of mixed dispersions of phosphatidylcholine and phosphatidic-acid.Stud. Biophys. 1977; 65: 99-105Google Scholar,3Gawrisch K. Arnold K. Nuhn P. et al.NMR and calorimetric studies of changes in phase transition of head group modified phospholipids.Chem. Phys. Lipids. 1977; 20: 285-293https://doi.org/10.1016/0009-3084(77)90069-xCrossref PubMed Google Scholar,4Arnold K. Gawrisch K. Volke F. 31P NMR investigations of phospholipids .2. Dipolar interactions and distinction of phases of different phospholipid water dispersions.Stud. Biophys. 1979; 76: 85-93Google Scholar,5Arnold K. Lösche A. Gawrisch K. 31P NMR investigations of phase-separation in phosphatidylcholine-phosphatidylethanolamine mixtures.Biochim. Biophys. Acta. 1981; 645: 143-148https://doi.org/10.1016/0005-2736(81)90522-8Crossref PubMed Scopus (58) Google Scholar,6Gawrisch K. Arnold K. Klose G. et al.Optical-NMR, dsc-NMR and 31P NMR investigations of phase-separation in phosphatidylcholine phosphatidylethanolamine mixtures.Stud. Biophys. 1982; 90: 131-132Google Scholar,7Petrov A.G. Gawrisch K. Möps A. et al.Optical detection of phase transitions in simple and mixed lipid-water phases.Biochim. Biophys. Acta. 1982; 690: 1-7https://doi.org/10.1016/0005-2736(82)90231-0Crossref PubMed Scopus (31) Google Scholar,8Volke F. Arnold K. Gawrisch K. The effect of hydration on the mobility of phospholipids in the gel state - a proton nuclear magnetic-resonance spin-echo study.Chem. Phys. Lipids. 1982; 31: 179-189https://doi.org/10.1016/0009-3084(82)90043-3Crossref Scopus (15) Google Scholar,9Arnold K. Lvov Y.M. Kertscher H.P. et al.Analysis of the phase-behavior of charged phospholipids by electrophoresis, X-ray and 31P NMR studies.Stud. Biophys. 1985; 107: 65-74Google Scholar,10Gawrisch K. Stibenz D. Halbhuber K.J. et al.The rate of lateral diffusion of phospholipids in erythrocyte microvesicles.Biochim. Biophys. Acta. 1986; 856: 443-447https://doi.org/10.1016/0005-2736(86)90135-5Crossref PubMed Scopus (9) Google Scholar,11Lvov Y.M. Mogilevsky L.Y. Arnold K. et al.The X-ray small-angle analysis of mesophases of charged phospholipids.Kristallografiya. 1986; 31: 345-349Google Scholar,12Gawrisch K. Parsegian V.A. Rand R.P. et al.Energetics of a hexagonal-lamellar-hexagonal-phase transition sequence in dioleoylphosphatidylethanolamine membranes.Biochemistry. 1992; 31: 2856-2864https://doi.org/10.1021/bi00126a003Crossref PubMed Scopus (137) Google Scholar,13Gawrisch K. Barry J.A. Ferretti J.A. et al.Role of interactions at the lipid-water interface for domain formation.Mol. Membr. Biol. 1995; 12: 83-88https://doi.org/10.3109/09687689509038500Crossref PubMed Scopus (43) Google Scholar,14Gawrisch K. Holte L.L. NMR investigations of non-lamellar phase promoters in the lamellar phase state.Chem. Phys. Lipids. 1996; 81: 105-116https://doi.org/10.1016/0009-3084(96)02576-5Crossref Scopus (59) Google Scholar). This groundbreaking work was interspersed with studies on the interactions of lipids with solvents, ions in membrane bathing solutions, and the interactions of an amphipathic peptide from the HIV spike protein C-terminal tail (4Arnold K. Gawrisch K. Volke F. 31P NMR investigations of phospholipids .2. Dipolar interactions and distinction of phases of different phospholipid water dispersions.Stud. Biophys. 1979; 76: 85-93Google Scholar,15Arnold K. Gawrisch K. Volke F. Interaction of Na+ ions with phospholipid liposomes - 23Na NMR approach.Stud. Biophys. 1978; 74: 17-18Google Scholar,16Gawrisch K. Arnold K. Volke F. et al.2D NMR studies of phosphate - water interaction in dipalmitoyl phosphatidylcholine - water-systems.Stud. Biophys. 1978; 74: 13-14Google Scholar,17Arnold K. Gawrisch K. Volke F. 31P NMR investigations of phospholipids .1. Dipolar interactions and the 31P NMR lineshape of oriented phospholipid-water dispersions.Stud. Biophys. 1979; 75: 189-197Google Scholar,18Arnold K. Losche A. Gawrisch K. 31P NMR investigations of phospholipids .4. Studies of mixtures of phosphatidylcholine with negatively charged ethyl phosphoric-acid.Stud. Biophys. 1981; 82: 27-33Google Scholar,19Gawrisch K. Möps A. Detection of phase-separation in lipid-D2O dispersions by 2D NMR measurements.Ann. Phys. 1981; 493: 364-369Crossref Scopus (1) Google Scholar,20Klose G. Gawrisch K. Lipid - water interaction in model - membranes.Stud. Biophys. 1981; 84: 21-22Google Scholar,21Arnold K. Pratsch L. Gawrisch K. Effect of poly(ethylene glycol) on phospholipid hydration and polarity of the external phase.Biochim. Biophys. Acta. 1983; 728: 121-128https://doi.org/10.1016/0005-2736(83)90444-3Crossref PubMed Scopus (92) Google Scholar,22Národa J. Balgavý P. Cizmárik J. et al.Effect of the local-anesthetic heptacaine hydrochloride on the structured water in model phosphatidylcholine membrane - 2D NMR and 31P NMR study.Gen. Physiol. Biophys. 1983; 2: 457-471PubMed Google Scholar,23Balgavý P. Gawrisch K. Frischleder H. Effect of N-Alkyl-N,N,N-trimethylammonium ions on phosphatidylcholine model membrane-structure as studied by 31P NMR.Biochimica et Biophysica Acta - Biomembranes. 1984; 772: 58-64https://doi.org/10.1016/0005-2736(84)90517-0Crossref Scopus (23) Google Scholar,24Frischleder H. Gabrielska J. Witek S. et al.Interaction of chosen quaternary ammonium-salts with phospholipid-membranes .1. Intercalation in phospholipid-bilayers.Stud. Biophys. 1984; 102: 15-22Google Scholar,25Arnold K. Herrmann A. Pratsch L. et al.Mechanisms of Peg-induced fusion.Stud. Biophys. 1985; 110: 135-141Google Scholar,26Arnold K. Herrmann A. Gawrisch K. et al.The dielectric-properties of aqueous-solutions of poly(ethylene glycol) and their influence on membrane-structure.Biochim. Biophys. Acta. 1985; 815: 515-518https://doi.org/10.1016/0005-2736(85)90381-5Crossref PubMed Scopus (105) Google Scholar,27Gawrisch K. Richter W. Klose G. et al.The influence of water concentration on the structure of egg-yolk phospholipid water dispersions.Stud. Biophys. 1985; 108: 5-16Google Scholar,28Klose G. Arnold K. Gawrisch K. et al.The structure and dynamics of water near membrane surfaces.Colloids Surf. 1985; 14: 21-30https://doi.org/10.1016/0166-6622(85)80038-XCrossref Scopus (26) Google Scholar,29Balgavý P. Gawrisch K. Hydration properties and structure of phosphatidylcholine membranes in the presence of normal-nonyl bromide.Gen. Physiol. Biophys. 1986; 5: 365-370PubMed Google Scholar,30Gawrisch K. Thunich R. Arnold K. et al.The influence of poly(ethylene glycol) on ion binding to membrane surfaces.Mol. Cryst. Liq. Cryst. 1987; 152: 333-341https://doi.org/10.1080/00268948708070963Crossref Google Scholar,31Gawrisch K. Janz S. The uptake of pristane (2,6,10,14-tetramethylpentadecane) into phospholipid-bilayers as assessed by NMR, Dsc, and tritium labeling methods.Biochim. Biophys. Acta. 1991; 1070: 409-418https://doi.org/10.1016/0005-2736(91)90081-ICrossref PubMed Scopus (9) Google Scholar,32Kertscher H.P. Ostermann G. Gawrisch K. et al.Paf-antagonists with phospholipid structure .1. Phospholipids with heteroarene head groups - synthesis, characterization and structure-activity requirements.Pharmazie. 1991; 46: 575-579PubMed Google Scholar,33Gawrisch K. Ruston D. Fuller N. et al.Membrane dipole potentials, hydration forces, and the ordering of water at membrane surfaces.Biophys. J. 1992; 61: 1213-1223https://doi.org/10.1016/S0006-3495(92)81931-8Abstract Full Text PDF PubMed Scopus (406) Google Scholar,34Janz S. Krumbiegel M. Gawrisch K. The fluidity of dopc bilayers and membrane-fractions prepared from murine plasmacytoma cells is unchanged after incorporation of pristane (2,6,10,14-tetramethylpentadecane) as assessed by fluorescence polarization analysis.Cancer Biochem. Biophys. 1992; 13: 85-92PubMed Google Scholar,35Meyer H.W. Tsvetkova N. Gawrisch K. et al.Structural organization of a lipid mixture from egg-yolk (active lipid) in nonhydrated state and in excess of water.Pharmazie. 1992; 47: 518-522Google Scholar,36Arnold K. Gawrisch K. Effects of fusogenic agents on membrane hydration: a deuterium nuclear magnetic resonance approach.Methods Enzymol. 1993; 220: 143-157https://doi.org/10.1016/0076-6879(93)20080-mCrossref PubMed Google Scholar,37Gawrisch K. Han K.H. Ferretti J.A. et al.Interaction of peptide fragment 828-848 of the envelope glycoprotein of human immunodeficiency virus type I with lipid bilayers.Biochemistry. 1993; 32: 3112-3118https://doi.org/10.1021/bi00063a024Crossref PubMed Scopus (67) Google Scholar,38Barry J.A. Gawrisch K. Effects of ethanol on lipid bilayers containing cholesterol, gangliosides, and sphingomyelin.Biochemistry. 1995; 34: 8852-8860https://doi.org/10.1021/bi00027a037Crossref PubMed Scopus (64) Google Scholar,39Koenig B.W. Bergelson L.D. Ferretti J.A. et al.Effect of the conformation of a peptide from gp41 on binding and domain formation in model membranes.Mol. Membr. Biol. 1995; 12: 77-82https://doi.org/10.3109/09687689509038499Crossref PubMed Scopus (14) Google Scholar,40Koenig B.W. Ferretti J.A. Gawrisch K. Site-specific deuterium order parameters and membrane-bound behavior of a peptide fragment from the intracellular domain of HIV-1 gp41.Biochemistry. 1999; 38: 6327-6334https://doi.org/10.1021/bi982800gCrossref PubMed Scopus (45) Google Scholar), and many papers on lipid syntheses and spectra of newly purified lipids (see supporting citations). His first two papers with Adrian Parsegian and Peter Rand and their colleagues were very influential. First, the study of the reentrant phase of phosphatidylethanolamine, a biphasic phase change between lamellar and inverse hexagonal phase with varying osmotic stress, led to a better understanding of lipid energetics under stress (12Gawrisch K. Parsegian V.A. Rand R.P. et al.Energetics of a hexagonal-lamellar-hexagonal-phase transition sequence in dioleoylphosphatidylethanolamine membranes.Biochemistry. 1992; 31: 2856-2864https://doi.org/10.1021/bi00126a003Crossref PubMed Scopus (137) Google Scholar). Second, the finding that the repulsive hydration force between bilayers originated from disruptions in the H-bonding network between waters bound to the phosphate and to embedded waters in the headgroup region had broad implications to the forces between other substances, such as DNA, carbohydrates, and proteins (33Gawrisch K. Ruston D. Fuller N. et al.Membrane dipole potentials, hydration forces, and the ordering of water at membrane surfaces.Biophys. J. 1992; 61: 1213-1223https://doi.org/10.1016/S0006-3495(92)81931-8Abstract Full Text PDF PubMed Scopus (406) Google Scholar). Klaus’s work with Sarah Keller and Sarah Veatch (41Veatch S.L. Polozov I.V. Keller S.L. et al.Liquid domains in vesicles investigated by NMR and fluorescence microscopy.Biophys. J. 2004; 86: 2910-2922https://doi.org/10.1016/S0006-3495(04)74342-8Abstract Full Text Full Text PDF PubMed Scopus (395) Google Scholar,42Veatch S.L. Gawrisch K. Keller S.L. Closed-loop miscibility gap and quantitative tie-lines in ternary membranes containing diphytanoyl PC.Biophys. J. 2006; 90: 4428-4436https://doi.org/10.1529/biophysj.105.080283Abstract Full Text Full Text PDF PubMed Scopus (165) Google Scholar,43Veatch S.L. Soubias O. Gawrisch K. et al.Critical fluctuations in domain-forming lipid mixtures.Proc. Natl. Acad. Sci. USA. 2007; 104: 17650-17655https://doi.org/10.1073/pnas.0703513104Crossref PubMed Scopus (344) Google Scholar) on the equilibrium of liquid-ordered (Lo) and liquid-disordered phases in bilayers had a profound influence on the field and set the stage for understanding lipid rafts in cell membranes. Quite remarkably, the first paper in this series went from a question they posed to Klaus at a Biophysical Society (BPS) subgroup meeting to a nearly fully formed story after only 2 weeks of research in Klaus’s lab, collecting spectra by day and trying to keep up with the analysis by night. Tie-line measurements extracted from NMR spectra brought Klaus’s characteristic rigor to semi-quantitative observations previously made using fluorescence microscopy while drawing connections to past studies on membranes of cholesterol and phospholipids. Subsequent measurements used NMR line broadening to identify fluctuations in membranes poised near miscibility critical points, an alternative mechanism for membrane organization on submicron length scales (43Veatch S.L. Soubias O. Gawrisch K. et al.Critical fluctuations in domain-forming lipid mixtures.Proc. Natl. Acad. Sci. USA. 2007; 104: 17650-17655https://doi.org/10.1073/pnas.0703513104Crossref PubMed Scopus (344) Google Scholar). Klaus then helped guide the simulation paper showing that the structure of the Lo phase consisted of patches of highly ordered (gel-like) saturated lipids with less ordered boundary regions of unsaturated lipid and cholesterol (44Sodt A.J. Sandar M.L. Lyman E. et al.The molecular structure of the liquid-ordered phase of lipid bilayers.J. Am. Chem. Soc. 2014; 136: 725-732https://doi.org/10.1021/ja4105667Crossref PubMed Scopus (166) Google Scholar). A few years later, Klaus took the electron paramagnetic resonance measurements showing that oxygen was nearly as likely to be in the midplanes of an Lo phase as the liquid disordered one, providing critical experimental support for simulations detailing the pathway of oxygen permeation through the Lo phase (45Ghysels A. Krämer A. Pastor R.W. et al.Permeability of membranes in the liquid ordered and liquid disordered phases.Nat. Commun. 2019; 10: 5616https://doi.org/10.1038/s41467-019-13432-7Crossref PubMed Scopus (43) Google Scholar). Klaus often responded to scientific questions by “this should be done with Kernresonanz” (using the German word for NMR spectroscopy). And of course, he really knew a way to utilize NMR to solve it. In the mid 90s, Klaus was one of the first to recognize how nuclear Overhauser enhancement spectroscopy (NOESY) could be adapted to lipid membranes using 1H magic angle spinning (MAS) (46Holte L.L. Gawrisch K. Determining ethanol distribution in phospholipid multilayers with MAS-NOESY spectra.Biochemistry. 1997; 36: 4669-4674https://doi.org/10.1021/bi9626416Crossref PubMed Scopus (121) Google Scholar). Klaus’s work with Daniel Huster converted 1H MAS NOESY into a tool for quantitative membrane structural studies and demonstrated that membranes are characterized by a tremendous degree of motional disorder (47Feller S.E. Huster D. Gawrisch K. Interpretation of NOESY cross-relaxation rates from molecular dynamics simulation of a lipid bilayer.J. Am. Chem. Soc. 1999; 121: 8963-8964https://doi.org/10.1021/ja991456nCrossref Scopus (98) Google Scholar,48Huster D. Arnold K. Gawrisch K. Investigation of lipid organization in biological membranes by two-dimensional nuclear overhauser enhancement spectroscopy.J. Phys. Chem. B. 1999; 103: 243-251https://doi.org/10.1021/jp983428hCrossref Scopus (151) Google Scholar,49Huster D. Gawrisch K. NOESY NMR crosspeaks between lipid headgroups and hydrocarbon chains: spin diffusion or molecular disorder?.J. Am. Chem. Soc. 1999; 121: 1992-1993https://doi.org/10.1021/ja9838413Crossref Scopus (91) Google Scholar,50Yau W.M. Gawrisch K. Lateral lipid diffusion dominates NOESY cross-relaxation in membranes.J. Am. Chem. Soc. 2000; 122: 3971-3972https://doi.org/10.1021/ja9944756Crossref Scopus (28) Google Scholar). Together with Bill Wimley and Steve White, Klaus used 1H MAS NOESY to show the preference of tryptophan for the membrane interface, which is to date his most highly cited paper (51Yau W.M. Wimley W.C. White S.H. et al.The preference of tryptophan for membrane interfaces.Biochemistry. 1998; 37: 14713-14718https://doi.org/10.1021/bi980809cCrossref PubMed Scopus (829) Google Scholar). Since then, the use of 1H MAS NOESY NMR has evolved into a major tool in the arsenal of NMR spectroscopists for the study of membrane binding, organization, localization, and orientation of membrane embedded molecules (52Feller S.E. Brown C.A. Gawrisch K. et al.Nuclear overhauser enhancement spectroscopy cross-relaxation rates and ethanol distribution across membranes.Biophys. J. 2002; 82: 1396-1404https://doi.org/10.1016/S0006-3495(02)75494-5Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar,53Gawrisch K. Eldho N.V. Polozov I.V. Novel NMR tools to study structure and dynamics of biomembranes.Chem. Phys. Lipids. 2002; 116: 135-151https://doi.org/10.1016/S0009-3084(02)00024-5Crossref PubMed Scopus (71) Google Scholar,54Gaede H.C. Yau W.M. Gawrisch K. Electrostatic contributions to indole-lipid interactions.J. Phys. Chem. B. 2005; 109: 13014-13023https://doi.org/10.1021/jp0511000Crossref PubMed Scopus (76) Google Scholar,55Kimura T. Cheng K. Gawrisch K. et al.Location, structure, and dynamics of the synthetic cannabinoid ligand CP-55,940 in lipid bilayers.Biophys. J. 2009; 96: 4916-4924https://doi.org/10.1016/j.bpj.2009.03.033Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar). Klaus’s work on 1H MAS NOESY NMR was also instrumental to what has been his lifetime interest: understanding how membranes rich in polyunsaturated lipids like DHA differ from less unsaturated ones. After early 2H NMR studies with Frances Separovic and Bernd Koenig on the influence of chain unsaturations on lipid bilayers (56Holte L.L. Peter S.A. Gawrisch K. et al.2H nuclear-magnetic-resonance order-parameter profiles suggest a change of molecular shape for phosphatidylcholines containing a polyunsaturated acyl-chain.Biophys. J. 1995; 68: 2396-2403https://doi.org/10.1016/S0006-3495(95)80422-4Abstract Full Text PDF PubMed Scopus (154) Google Scholar,57Holte L.L. Separovic F. Gawrisch K. Nuclear magnetic resonance investigation of hydrocarbon chain packing in bilayers of polyunsaturated phospholipids.Lipids. 1996; 31: S199-S203https://doi.org/10.1007/BF02637076Crossref PubMed Google Scholar,58Separovic F. Gawrisch K. Effect of unsaturation on the chain order of phosphatidylcholines in a dioleoylphosphatidylethanolamine matrix.Biophys. J. 1996; 71: 274-282https://doi.org/10.1016/S0006-3495(96)79223-8Abstract Full Text PDF PubMed Scopus (58) Google Scholar,59Koenig B.W. Strey H.H. Gawrisch K. Membrane lateral compressibility determined by NMR and X-ray diffraction: effect of acyl chain polyunsaturation.Biophys. J. 1997; 73: 1954-1966https://doi.org/10.1016/S0006-3495(97)78226-2Abstract Full Text PDF PubMed Scopus (245) Google Scholar), Klaus told us why bilayers with high DHA content have low order (60Feller S.E. Gawrisch K. MacKerell A.D. Polyunsaturated fatty acids in lipid bilayers: intrinsic and environmental contributions to their unique physical properties.J. Am. Chem. Soc. 2002; 124: 318-326https://doi.org/10.1021/ja0118340Crossref PubMed Scopus (380) Google Scholar), how the loss of one double bond affects bilayer properties (61Eldho N.V. Feller S.E. Gawrisch K. et al.Polyunsaturated docosahexaenoic vs docosapentaenoic acid - differences in lipid matrix properties from the loss of one double bond.J. Am. Chem. Soc. 2003; 125: 6409-6421https://doi.org/10.1021/ja029029oCrossref PubMed Scopus (195) Google Scholar), and how polyunsaturation may affect protein function (62Feller S.E. Gawrisch K. Woolf T.B. Rhodopsin exhibits a preference for solvation by polyunsaturated docosohexaenoic acid.J. Am. Chem. Soc. 2003; 125: 4434-4435https://doi.org/10.1021/ja0345874Crossref PubMed Scopus (90) Google Scholar,63Soubias O. Teague W.E. Gawrisch K. Evidence for specificity in lipid-rhodopsin interactions.J. Biol. Chem. 2006; 281: 33233-33241https://doi.org/10.1074/jbc.M603059200Abstract Full Text Full Text PDF PubMed Scopus (80) Google Scholar) and membrane fusion events (64Teague W.E. Fuller N.L. Gawrisch K. et al.Polyunsaturated lipids in membrane fusion events.Cell. Mol. Biol. Lett. 2002; 7: 262-264PubMed Google Scholar). Klaus’s work over the past 30 years has been foundational to our understanding of the biophysical properties of polyunsaturated lipid bilayers (59Koenig B.W. Strey H.H. Gawrisch K. Membrane lateral compressibility determined by NMR and X-ray diffraction: effect of acyl chain polyunsaturation.Biophys. J. 1997; 73: 1954-1966https://doi.org/10.1016/S0006-3495(97)78226-2Abstract Full Text PDF PubMed Scopus (245) Google Scholar,61Eldho N.V. Feller S.E. Gawrisch K. et al.Polyunsaturated docosahexaenoic vs docosapentaenoic acid - differences in lipid matrix properties from the loss of one double bond.J. Am. Chem. Soc. 2003; 125: 6409-6421https://doi.org/10.1021/ja029029oCrossref PubMed Scopus (195) Google Scholar,65Huster D. Jin A.J. Gawrisch K. et al.Water permeability of polyunsaturated lipid membranes measured by O-17 NMR.Biophys. J. 1997; 73: 855-864https://doi.org/10.1016/S0006-3495(97)78118-9Abstract Full Text PDF PubMed Scopus (175) Google Scholar,66Huster D. Arnold K. Gawrisch K. Influence of docosahexaenoic acid and cholesterol on lateral lipid organization in phospholipid mixtures.Biochemistry. 1998; 37: 17299-17308https://doi.org/10.1021/bi980078gCrossref PubMed Scopus (242) Google Scholar,67Mitchell D.C. Gawrisch K. 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