Tetra-alanine

Calculating values of a according to (91) is difficult in general because the Hessian matrices H v/exi depend on x. A simplified method of calculating a is to start with small values of af (e.g., a = 5) and increase the values of a until no new solutions are found. This can be a practical solution to many problems where the correct values of a are difficult to determine. However, this method has the one serious drawback in that it sacrifices the theoretical guarantee of finding all solutions. In spite of this fact, we were able to identify all minima and first-order transition states using modest values of a for alanine, alanine dipeptide, and tetra-alanine. Tetra-alanine will be discussed in Section IV.C. 

Tropoelastin is the soluble precursor of elastin and consists of alternating hydrophobic and hydrophilic peptide domains. The most common amino acids in the hydrophobic domains are Gly, Val, Ala, and Pro, which are often present in repeats of tetra-, penta-, and hexapeptides, such as Gly-Gly-Val-Pro, Gly-Val-Gly-Val-Pro, Gly-Val-Pro-Gly-Val, and Gly-Val-Gly-Val-Ala-Pro, respectively [3, 4]. The hydrophilic domains are mainly composed of lysines interspersed by alanines. 

The electron transfer reaction in Reaction 6 was measured by circular dichroism stopped-flow methods at pH 7.7. Only the tetra-L-alanine... 

Both dipolar and contact contributions are important in glycinate complexes. (166) U(iv) complexes with a-alanine, (167) various amino-acids, (168) ethyl trifluoroacetoacetate, (169) tetrakis-(tetra-ethylammonium)octathiocyanatouranate U(NCS)g(NEt4)4, (170) and -diketones (171, 172) have been examined. In studying the ligand exchange kinetics of the latter complexes (172) the mechanism is considered to involve a ninth coordination site in the U(iv) chelate. 

Figure 32.3 Turnover time for the fluorescent compound LYA-tetra-alanine by cultures of different phytoplankton species and taxa (data from Mulholland and Lee, in revision).

Fluoro-2,4-dinitrophenyl-5-L-alanine amide (Marfey s reagent) and 2..3.4.6-tetra-0-aeetyl-P-D-gluer>pyranosyl isothkKyanatc... 

Inhib. abbrev. DTT = dithioghreitol E64D = epoxysuccinyl-L-leucyl-amido-3-methyl-butane ethyl ester EDTA = ethylene-diamine-tetra-acetic acid EGTA = ethylen-glycol-tetra-acetic acid LHVS = morpholinurea-leucine-homophenyl-alanine-vinylsulfone-phenyl NEM = N-ethyl-maleimide PAI = plasminogen activator inhib. PMSF = phenil-methyl-sulfonil fluoride SBTl = soybean trypsin inhib. TIMP = tissue inhib. of metalloproteinases TPCK = tosyl-L-phenyl-alanyl-chloro-methane Al.so termed stephins. 

Perhaps the interplay between sugar amino acids and a-amino acids is more clearly demonstrated in the synthesis of a-D-glucosyl-(i )-alanine reported by Axon and Beckwith [33]. In the reaction, (27 )-methyleneoxazolidinone was treated with 2,3,4,6-tetra-O-acetyl glucosyl iodide in the presence of sodium cyanoborohydride and tributyltin chloride to give the a-C-glycoside in 88% yield (Fig. 15). 

FIGURE 3.4 Illustration of the process of acquiring a one-dimensional NMR spectrum. The steps involved in obtaining an NMR spectrum are shown. The sample is a tetra-peptide (Val-Ala-Ser-Ala). A short (10 asec) intense RF pulse is applied to the sample. This pulse excites all of the nuclei and they emit energy at their characteristic absorption frequencies. This signal is called the free induction decay (FID) and is collected as a function of time. This time domain signal is converted to spectrum by Fourier transformation. Note the characteristic chemical shifts for amide protons (H v), a-protons, (i-protons, and methyl protons. Also note that the two alanine residues, although chemically equivalent, have different chemical shifts because they experience different local environments. 

Pilz, I., Kratky, O., Licht, A., and Sela, M. (1975) Shape and volume of fragments Fab and F(ab )2 of anti-poly(D-alanyl) antibodies in the presence and absence of tetra-D-alanine as determined by small-angle x-ray scattering. Biochemistry 14,1326-1333. 

CoX NHj) ] + (X = H20, nitrile, glycine, alanine ) and [Co(en)2(L-L)]"+ (L-L = thiolate, thioether, alkoxy, carboxylate) by [Ru(NH3)6]"+ has been studied kinetically, the specific rates for reduction of the nitrile complexes being increased due to electron withdrawal by the C=N moiety. For the glycine and alanine complexes, no pH dependence was observed, the electron transfer being thought not to occur via coordination of carboxylate to ruthenium. Kinetic studies have also been carried out on the reduction of [Fe(L)(OH2)2] (L = tetra-4-iV-methylpyridyl por-phine), [Fe(edta)] , cytochrome aa3, cytochrome c(III), platinum(IV) and copper(ll)/ complexes and perchlorate salts.The reduction of Fe " is found to be faster than that of [FeOHf. The importance of non-adiabaticity in the above outer-space mechanisms has been discussed. ... 

A methanolic soln. of L-alanine methyl ester, anhydrous CuClg, and triethylamine stirred 3 hrs. at room temp., and the product isolated as the N-carbobenzoxy deriv. -> N-carbobenzoxy-L-alanyl-L-alanine methyl ester. Y 34.5%. F. e., also tri- and tetra-merization, s. S. Yamada, S. Terashima, and M.Wagatsuma, Tetrah. Let. 1970, 1501. 

Alitame [II] is nutritive, but due to its intense sweetness, the amounts used are small enough for it to be considered and classified as a nonnutritive sweetener. Alitame is formed from the amino acids L-aspartic acid and o-alanine with a novel amide moiety (formed from 2,2,4,4-tetra-methylthienanylamine). Alitame exhibits superior stability under a variety of conditions because of its unique amide group. Alitame has been approved... 

T. Asakura, K. Yazawa, K. Horihuchi, F. Suzuki, Y. Nishiyama, K. Nishimura, H. Kaji, Difference in the structmes of alanine tri- and tetra-peptides with antiparallel p-sheet assessed by X-ray diffraction, solid-state NMR and chemical shift calculations by GIPAW, Biopolymers 101 (2014) 13—20. 

The monofimctional tetra-iridium cluster 45 synthesized according to Scheme 6.11 was used to label the capsid of HBV assembled from a mutant protein where the cysteines of the wild-type protein had been replaced by alanine and an additional cysteine appended at the C terminus. 

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