This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. We have been studying the molecular mechanism of the main phase transition (the gel to liquid crystalline phase transition) of lipid bilayers. Previously, we observed the quasicritical fluctuation in DOPC bilayers around Tc. During the past year, we improved the simulations of ESR spectra of the head group spin label DPP-Tempo and chain spin labels 5PC and 14PC in DMPC bilayers around Tc at 23C. Two components are required for a satisfactory fit of the spectra from 5PC and 14PC, which is consistent with previous ESR and NMR studies on the main phase transition of lipid bilayers. When the temperature of a DMPC dispersion is cooled down from 30C to 15C, changes of the dynamic ordering of the two components are quite different. Order parameters S0 of the second component of 5PC and 14PC spectra show a strong critical phenomenon around the Tc. For example, S0 of 5PC sharply drops from 0.591at 24.0C to -0.457 at 23.3C, then jumps to 0.903 at 22C. These changes are characteristic of a second order phase transition. In contrast, there is nearly no change or a slight change in S0 around Tc for first component. We also observed a divergence in the linewidth of 5PC and 14PC spectra around the Tc, which is also a sign of a second order phase transition. Unlike the spectra of 5PC, the spectra of DPP-Tempo in DMPC can be fit very well with only a single component, and the variation of the S0 with temperature exhibits a cusp-like pattern around Tc, similar to that we previously observed for DPP-Tempo in DOPC around Tc. This is also a critical phenomenon. Interestingly, the tip of the cusp is located at 24.4C, which slightly deviates from Tc. The rotational diffusion rates R perpendicular and R parallel of the second component for both 5PC and 14PC drop precipitously at 23.3C (by factors of more than 100). The population of the first (second) component decreases (increases) with decreasing temperature only gradually below and above the Tc, but drops (jumps) around the Tc from ~0.8(~ 0:2) to 0.5(~0.5). According to IR studies of the main phase transition of lipid bilayers, the two populations may represent lipids which have two different acyl chain conformations, thus they have two different packing modes in the bilayers. This type of temperature variation of two lipid populations signifies a first order phase transition at Tc. However, overall the main phase transition of DMPC bilayers is a weak first order phase transition, because of concomitant strong critical phenomena.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
2P41RR016292-11
Application #
8363978
Study Section
Special Emphasis Panel (ZRG1-BCMB-K (40))
Project Start
2011-09-01
Project End
2012-08-31
Budget Start
2011-09-01
Budget End
2012-08-31
Support Year
11
Fiscal Year
2011
Total Cost
$803
Indirect Cost
Name
Cornell University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
872612445
City
Ithaca
State
NY
Country
United States
Zip Code
14850
Jain, Rinku; Vanamee, Eva S; Dzikovski, Boris G et al. (2014) An iron-sulfur cluster in the polymerase domain of yeast DNA polymerase ?. J Mol Biol 426:301-8
Pratt, Ashley J; Shin, David S; Merz, Gregory E et al. (2014) Aggregation propensities of superoxide dismutase G93 hotspot mutants mirror ALS clinical phenotypes. Proc Natl Acad Sci U S A 111:E4568-76
Georgieva, Elka R; Borbat, Peter P; Ginter, Christopher et al. (2013) Conformational ensemble of the sodium-coupled aspartate transporter. Nat Struct Mol Biol 20:215-21
Airola, Michael V; Sukomon, Nattakan; Samanta, Dipanjan et al. (2013) HAMP domain conformers that propagate opposite signals in bacterial chemoreceptors. PLoS Biol 11:e1001479
Airola, Michael V; Huh, Doowon; Sukomon, Nattakan et al. (2013) Architecture of the soluble receptor Aer2 indicates an in-line mechanism for PAS and HAMP domain signaling. J Mol Biol 425:886-901
Sun, Yan; Zhang, Ziwei; Grigoryants, Vladimir M et al. (2012) The internal dynamics of mini c TAR DNA probed by electron paramagnetic resonance of nitroxide spin-labels at the lower stem, the loop, and the bulge. Biochemistry 51:8530-41
Yu, Renyuan Pony; Darmon, Jonathan M; Hoyt, Jordan M et al. (2012) High-Activity Iron Catalysts for the Hydrogenation of Hindered, Unfunctionalized Alkenes. ACS Catal 2:1760-1764
Dzikovski, Boris; Tipikin, Dmitriy; Freed, Jack (2012) Conformational distributions and hydrogen bonding in gel and frozen lipid bilayers: a high frequency spin-label ESR study. J Phys Chem B 116:6694-706
Gaffney, Betty J; Bradshaw, Miles D; Frausto, Stephen D et al. (2012) Locating a lipid at the portal to the lipoxygenase active site. Biophys J 103:2134-44
Maeda, Kiminori; Lodge, Matthew T J; Harmer, Jeffrey et al. (2012) Electron tunneling in lithium-ammonia solutions probed by frequency-dependent electron spin relaxation studies. J Am Chem Soc 134:9209-18

Showing the most recent 10 out of 72 publications