Alanine, tetramer

A set of low-energy conformers has been provided for alanine (R=CH3) tetramer (terminated at both ends by amide functionality). For each conformer, identify each of the a carbons and measure the (j) and v(/ dihedral angles (see table below). 

When these acidic residues where mutated to alanine (neutral) or lysine (positive), rates of inactivation were affected. The largest effect took place with the positive amino acid mutation. The authors found that mutations in the inactivation peptide are tied to those in the Tl-Sl linker near the T1 domain in other words, the inactivation peptide must be near the Tl-Sl linker when it inactivates the pore. The conclusion reached is that since the inactivation peptide cannot fit through the center of the TI4P4 complex, it must reach the ion conduction pore through lateral openings above the T1 tetramer. 

The 37-kDa 334-residue subunits of the dimeric type I tryptophanyl-tRNA synthetase238 are the smallest known the largest bacterial synthetase is an alanine-specific type II tetramer with 95-kDa 875-residue subunits.239 Gene deletions show that a much smaller core, comparable in size to that of the tryptophanyl-tRNA synthetase, is needed for amino acid activation. The synthetases share little sequence homology except for a short 11-residue part of the adenylate binding site near the N terminus.240 241 Some of the synthetases contain bound zinc ions.225,242... 

A pH-dependent dissociation of the tetramer to dimers of molecular weight 64,000 occurred between pH 2 and 7. Analysis of the C-terminal amino acid showed both alanine and leucine, and the N-terminus was valine. The possibility of multiple isolectins was indicated by multiple band-formation of isoelectric-focused hemagglutinin.611... 

O2IOSC7HS, Osmium, dicarbonyI(Ti -cycIo-pentadienyI)iodo-, 25 191 02lOsC,2H,s, Osmium, dicarbonyliodo(Ti -pentamethylcyclopentadienyl)-, 25 191 O2NC2HS, Glycine cobalt complex, 25 135 02NC3Ht, Alanine cobalt complex, 25 137 02N4P2QH,2, 1 W,5W-[1, 4,2,3]Diazadiphos-phoIo[2,3-b][l,4,2,3]diazadiphosphoIe-2,6-(3W,7W)-dione, 1,3,5,7-tetrame-thyl-, 24 122... 

The involvement of specific residues in the determination of conductance properties of the protein is readily addressed by use of the synthetic proteins. Accordingly, a tethered tetramer of M2 8 segments in which serine-8 is replaced with alanine was synthesized. This analog, T4M28(S - A), also forms channels in PC membranes with a single-channel conductance in symmetric 0.5-M KCl of 20 pS (49), lower than the 24 pS observed with T4M28. These results are in accord with observations obtained with site-directed mutagenesis of rodent acetylcholine receptors (72). 

Taillefumier et al. were the first to report on cyclic j8-peptoids and described macrocycles comprised of A-propargyl-j8-alanine oligomers 44. " The cyclic tetramer was... 

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