2023年11月23日 · Methionine is an essential amino acid which contains sulphur and which has the ability to 'donate' part of its structure to other molecules, thus altering them. It is therefore called a 'methyl donor'.

The subject developed postload plasma concentrations of methionine far beyond those reported previously in humans given the usual oral loading dose of methionine (100 mg/kg body wt). Her preload plasma metabolite values rule out known genetic diseases that might predispose one to unusually high methionine concentrations.

Methionine (abbreviated as Met or M; encoded by the codon AUG) is an α- amino acid that is used in the biosynthesis of proteins. It contains a carboxyl group (which is in the deprotonated −COO − form under biological pH conditions), an amino group (which is in the protonated −NH+.

L-蛋氨酸,又名L- 甲硫氨酸，是蛋氨酸的 左旋体，化学式为C5H11NO2S， 化学性质 为无色或白色有光泽片状结晶或白色 结晶性 粉末,稍带特殊气味,味微苦。 熔点280～281℃。 对 强酸 不稳定,可导致 脱甲基作用。 溶于水 (5.6g/100mL,30℃)、温热的稀 乙醇 、碱性溶液或稀无机酸。 难溶于乙醇,几乎不溶于 乙醚。 毒性: LD50 29mmol/kg (大鼠, 腹腔注射)。 特别应注意的是在蛋氨酸 生产过程 中使用剧毒原料 氰化钠，因此生产车间应按氰化钠毒性 防护要求，采取相应措施：设备应 …

This indicates that the α-amino group is essentially fully protonated (has gained H +) and exists in the –NH 3 + state at pH 7.0. Therefore, the backbone portion of a free amino acid at pH 7 is best represented as: + NH3-CHR-COO – When an amino acid is linked up as part of a peptide chain, the situation is different.

The average charge of methionine at pH 7 is simply the sum of these mole fractions, accounting for the charge of each species, and is approximately equal to -0.006109. I assume your textbook is rounding. You can plot these functions to see how charge varies with pH: Your answer is very detailed and interesting.

The charges of the given amino acids at pH 7 are: Methionine: 0; Phenylalanine: 0; Proline: 0; Serine: -1; Explanation: At pH 7, the charge of an amino acid can be determined by comparing the pH to the pKa values of its ionizable groups. The pKa values represent the pH at which half of the ionizable groups are protonated and half are deprotonated.

At pH 7, the amino acid is a zwitterion, or dipolar ion. A unique side chain, or R group, characterizes each amino acid. Amino acids are polymerized by condensation reactions to form a chain called a polypeptide.

STRUCTURES OF AMINO ACIDS at pH 7.0 Author: Michelle Mischke Created Date: 1/6/2012 7:43:45 PM ...

Absorbance and pH relationship for methionine. [...] Camborough PIC sows (n = 291) were fed 1 of 5 dietary treatments to evaluate the standardized ileal digestible (SID) Thr:Lys requirement...