Peptide, tri

Cyclic tri (cis L-proline). The crystal structure of the cyclic peptide tri cis L-proline) was determined by Kartha et al. [33]. This molecule contains four ring closures. We felt that a study of this structure would allow us to determine how well our program reproduces deviations from ideal geometry and would have intrinsic merit as a study of a minimodel of protein structure. 

An example of the first type is the nthesis of cystine peptides. Tri-Cys-Cys-Ala-0-CHj-( was synthesized on a Merrifield polymer. 

Stability of ttT tophan to anhydrous HF (Sakaldbara et al., 1967) was confirmed when two tryptophanyl peptides, Try-Phe and Try-Leu-Met-Asn-Thr, were synthesized by the solid-phase method and cleaved both by HF and HBr/TFA. In both cases the material resulting from the HF cleavage appeared to have less tryptophan degradation as evidenced spectrophotometrically and by TLC. 

Folic acid and its derivatives (mostly the tri-and heptaglutamyl peptides) are widespread in nature. It is a specific growth ctor for certain micro-organisms, but in animals the intestinal bacteria provide the small quantities needed for growth. The coenzyme forms are actually... 

One starts with individual amino adds or with peptides and tries to achieve the regioselective formation of a new amide bond. In its most general form such syntheses of peptides involve the following stages ... 

Short chains of amino acid residues are known as di-, tri-, tetrapeptide, and so on, but as the number of residues increases the general names oligopeptide and polypeptide are used. When the number of chains grow to hundreds, the name protein is used. There is no definite point at which the name polypeptide is dropped for protein. Twenty common amino acids appear regularly in peptides and proteins of all species. Each has a distinctive side chain (R in Figure 45.3) varying in size, charge, and chemical reactivity. 

Tri.-nethylsilyl triflate (TMSOTf), PhSCH, CF3COOH. These conditions also cleave the following protective groups used in peptide synthesis (MeO)Z-, Bn-, Ts-, CI2C6H3CH2-, BOM (benzyloxymethyl)-, Mts-, MBS-, r-Bu-SR, Ad-SR, but not a BnSR, Acm, or Arg(N02) group. The rate of cleavage is reported to be faster than with TfOH/TFA. 

For most free amino acids and small peptides, a mixture of alcohol with water is a typical mobile phase composition in the reversed-phase mode for glycopeptide CSPs. For some bifunctional amino acids and most other compounds, however, aqueous buffer is usually necessary to enhance resolution. The types of buffers dictate the retention, efficiency and - to a lesser effect - selectivity of analytes. Tri-ethylammonium acetate and ammonium nitrate are the most effective buffer systems, while sodium citrate is also effective for the separation of profens on vancomycin CSP, and ammonium acetate is the most appropriate for LC/MS applications. 

Class IIHLA molecules are expressed on the surface of antigen-presenting cells. They play a key role in presentation of processed linear peptide antigens of at least nine amino acids to T cells. Antigen is bound to the HLA antigen binding cleft formed by the a and 3 chains of the HLA class II molecule. This tri-molecular HLA-antigen complex binds in turn to the variable portion of the T-cell receptor. 

Bentin T, Nielsen P.E. Combined tri-plex/duplex invasion of double-stranded DNA by Tail-Clamp peptide nucleic acids (PNA). (Submitted)... 

Fig. 31 Interaction of a peptide-diacetylene (as structure 2 above, but with the NHCOCH3 replaced by NHCOCH2CH2COOCH3) with an AFM tip. Left. The AFM tip has broken a fibril that had no UV crosslinked diacetylenes while trying to move it. Middle and right UV crosslinking allows manipulation with the AFM tip without damaging the fibril. Adapted with permission from Jahnke et al. [71]. Copyright Wiley-VCH...

FIGURE 8. The reduction of fMet(O)-Leu-Phe by a human neutrophil and purified E. coli Met(O) peptide reductase. Each assay contained in a final volume of 30 /j1 25 mM Tris-HCl (pH 7.4), lOmM MgCl, 15 mm dithiothreitol 540pmole fMet(O)-[ H]Phe-Leu and Met(0)-peptide reductase. After incubating at 37 °C for 60 min, the incubation mixture is acidified and extracted with ethyl acetate. After centrifugation, an aliquot of the organic phase is removed and assayed for radioactivity. Reproduced by permission of Academic Press from Fliss and coworkers ... 

A review on TLC and PLC of amino adds, peptides, and proteins is presented in the works by Bhushan [24,25]. Chromatographic behavior of 24 amino acids on silica gel layers impregnated tiraryl phosphate and tri-n-butylamine in a two-component mobile phase (propanol water) of varying ratios has been studied by Sharma and coworkers [26], The effect of impregnation, mobile phase composition, and the effect of solubility on hRf of amino acids were discussed. The mechanism of migration was explained in terms of adsorption on impregnated silica gel G and the polarity of the mobile phase used. 

Chemical-shift Differences of the Amino Acid Carbon Atoms of a-Glycosylated and Nonglycosylated Di- and Tri-peptides... 

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