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. In previous work on channel formation using spin labeled Gramicidin A (GAsl) we found that the non-channel form prevails in the gel phase of mismatching lipids (DPPC, DSPC). We have now addressed the assignment of non-channel forms and studied the complex equilibrium in the gramicidin/lipid system, which includes channels (i.e. head-to-head dimers [HHD]), non-channel dimers, and monomers. To study non-channel forms of spin labeled GA, which can aggregate, we labeled two different sites on the same gramicidin molecule, instead of measuring the distance between spin labels attached at the same position on both dimer-forming molecules. This intramolecular distance between the spin labels could be used as a fingerprint of the particular conformation. Interactions between spin labels on different gramicidin molecules were eliminated by substantially diluting the double spin-labeled gramicidin by unlabeled gramicidin. Several new spin labeled gramicidin compounds were synthesized and used. In octanol, gramicidin exists mainly as a double helical (DH) left-handed antiparallel dimer, and we determined interspin distances for this structure. GAD with both N- and C-termini labeled and GALN, single-labeled at the N-terminus, substantially impair their propensity to HHD formation. In most lipids we observed two different conformations of GAD. The interspin distance in the main fraction (20.0?) is consistent with the monomeric state. Double helices (31.6?, exactly as in octanol) are a minor component with the fraction changing in the saturated lipid series in the following order: DLPC

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Biotechnology Resource Grants (P41)
Project #
2P41RR016292-11
Application #
8363972
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
$5,730
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
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