My research is on the dynamics and function of the molecules of
biological membranes. The emphasis is on understanding the unique
design of specific lipids that facilitate protein and membrane
functions in living cells.
I) Cellular membranes, along with ATP, are dominant in the energy
handling of living cells. This is due to proton gradients or, in the
case of the animal plasma membrane, sodium gradients. Proton leaks
waste energy stored in the ubiquitous proton gradients. A proposed
mechanism (1) for proton leakage suggests how lipids may be designed to
inhibit the waste. Our experiments are designed to challenge the model,
which predicts that stuffing the center of the bilayer with hydrocarbon
inhibits the leakage. Using neutron diffraction to show what is in the
bilayer center, together with fluorescence measurements of the leakage
rate across vesicles, we are confirming this for a wide variety of
natural lipids. The model predicts, for example, that the role of plant
sterols is to inhibit proton leaks whereas the role of cholesterol
is to inhibit sodium leaks. Heat shock proteins (HSP's) result from
cellular ATP deficiency. If sterols inhibit cation leaks through the
plasma membrane then their absence requires increased ATP consumption.
A drop in the ATP levels should produce HSP's.
a) Fluorescent measurements of proton leak inhibition by selected natural lipids.
(Together with D. Deamer, Santa Cruz, California)
b) Neutron diffraction measurements with D-substituted lipids; locates them in bilayers.
(Together with N. Dencher, Berlin, Germany)
c) Measuring gramicidin ion transport in the natural bilayers of the prokaryote that makes it.
(Together with O. Andersen, Cornell Med. School, NYC & N. Dencher, Berlin, Germany)
d) Seeking heat shock proteins in yeast with ergosterol deficiency; shows it creates ATP defic.
(Together with G. Small in the Biology Dept., CCNY)
e) Seeking HSP's in mammalian cells with cholesterol defic., if it results from Na leakage.
II) A second area is focused on the role of cardiolipin
(CL) in oxidative phosphorylation. This lipid is only found where
oxidative phosphorylation occurs in membranes. Our model (2) suggests
that cardiolipin plays two roles. It conducts/buffers protons in its headgroup domain and it assembles the proton pumps and the FoF1 ATPase into a membrane patch that operates as a multienzyme complex creating proton gradients and converting the energy into ATP.
a) Measuring lateral proton movement through headgroups of monolayers with lasers.
(in cooperation with N. Dencher, Berlin, Germany)
b) Using fluorescence microscopy to find CL patches in mitochondria.
III) A third area is on the function of polyunsaturated fatty acids
(PUFA's) in membrane signaling. The model views the function of PUFA's
as altering the thickness of the bilayer. When proteins alter their
thickness with respect to the bilayer in the presence of PUFA's the
lipids facilitate lateral wave motion. This permits neighboring
proteins to interact cooperatively. For example a heptahelical protein will communicate through the bilayer lipids to a G-protein
provoking GDP/GTP exchange. This amplifies the signal. For example
rhodopsin in the visual system activates 500 G-proteins on a
microsecond timescale. This membrane has mostly C22:6 fatty acids, the
most polyunsaturated fatty acid in mammals. Altering bilayer thickness
controlled by proteins means waves. For the rhodopsin model the wave is
a moving one. So also is the action potential. Clusters of transport
proteins, such as the Ca pump of the sarcoplasmic reticulum, that alter
thickness will yield standing waves.
a) Seeking surface waves in purple membrane activated by light with Xray scattering.
(Together with M. Tolan, Dormund, Germany & N. Dencher, Berlin, Germany)
Hauss, T., Dante, S., Dencher, N.A., Haines, T.H. "Squalane is in the
midplane of the lipid bilayer: implications for its function as a
proton permeability barrier", Biochim. Biophys. Acta, 1556:149-154 [PDF]
Haines, T.H., Dencher, N.A. "Cardiolipin: a proton trap for oxidative phosphorylation", FEBS Letters, 528, 35-39 (2002) [PDF]
Haines, T. "Do sterols reduce proton and sodium leaks through lipid bilayers?",
Prog. Lipid Res., 40, 299-324 (2001) [PDF]
Mileykovskaya E. et al. "Cardiolipin binds nonyl acridine orange by
aggregating the dye at exposed hydrophobic domains on bilayer
surfaces", FEBS Lett., 507:187 (2001). [PDF]
Less recent publications
Kates M, Syz JY, Gosser D, Haines TH. "pH-dissociation characteristics
of cardiolipin and its 2'-deoxy analogue", Lipids 28, 877-882 (1993) [Medline abstract][PDF]
Haines TH. "Anionic lipid headgroups as a proton-conducting pathway
along the surface of membranes: A hypothesis", PNAS 80, 160-4 (1983) [PDF]
Paula S, Volkov AG, van Hook AN, Haines TH, Deemer DW "Permeation of
proteins, K ions, and small polar molecules through phospholipid
bilayers as a function of membrane thickness", Biophys. J. 70, 939-948