- Tritium labelling of a cholesterol amphiphile designed for cell membrane anchoring of proteins
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Cell membrane association of proteins can be achieved by the addition of lipid moieties to the polypeptide chain, and such lipid-modified proteins have important biological functions. A class of cell surface proteins contains a complex glycosylphosphatidylinositol (GPI) glycolipid at the C-terminus, and they are accumulated in cholesterol-rich membrane microdomains, that is, lipid rafts. Semisynthetic lipoproteins prepared from recombinant proteins and designed lipids are valuable probes and model systems of the membrane-associated proteins. Because GPI-anchored proteins can be reinserted into the cell membrane with the retention of the biological function, they are appropriate candidates for preparing models via reduction of the structural complexity. A synthetic headgroup was added to the 3β-hydroxyl group of cholesterol, an essential lipid component of rafts, and the resulting cholesterol derivative was used as a simplified GPI mimetic. In order to quantitate the membrane integrated GPI mimetic after the exogenous addition to live cells, a tritium labelled cholesterol anchor was prepared. The radioactive label was introduced into the headgroup, and the radiolabelled GPI mimetic anchor was obtained with a specific activity of 1.37 TBq/mmol. The headgroup labelled cholesterol derivative was applied to demonstrate the sensitive detection of the cell membrane association of the anchor under in vivo conditions.
- Sch?fer, Balzs,Orbn, Erika,Kele, Zoltn,T?mb?ly, Csaba
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- RING INVERSION EQUILIBRIA IN 4-CHLORO-, 4-BROMO-, AND 4-METHOXY-1-ALKYLPIPERIDINES IN A NON-POLAR SOLVENT
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The position of ring inversion equilibrium (axial Requuatorial R) in 4-R-N-alkylpiperidines (R = Cl, Br, or OMe), dissolved in CFCl3-CDCl3, has been determined by (13)C n.m.r. spectroscopy at low temperatures.In all three series, change of NH to NMe produces a marked increase in the proportion of conformation with axial R.When R is OMe, further alterations in the N-substituent from Me to Et, Pri, and CH2CF3 do not affect the equilibrium significantly, but the signifficant changes observed when R is halogen can be related to the inductive effect of the N-substituent. (13)C Chemical shifts, proportions of conformations, and conformational free energy differences are recorded for all systems studied.
- Bailey, Judith M.,Booth, Harold,Al-Shirayda, Hatif A.R.Y.,Trimble, Mary L.
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p. 737 - 744
(2007/10/02)
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