The chalcogen elements oxygen, sulfur, and selenium are essential constituents of side chain functions of natural amino acids. Conversely, no structural and biological function has been discovered so far for the heavier and more metallic tellurium element. In the methionine series, only the sulfur‐containing methionine is a proteinogenic amino acid, while selenomethionine and telluromethionine are natural amino acids that are incorporated into proteins most probably because of the tolerance of the methionyl‐tRNA synthetase; so far, methoxinine the oxygen analogue has not been discovered in natural compounds. Similarly, the chalcogen analogues of tryptophan and phenylalanine in which the benzene ring has been replaced by the largely isosteric thiophene, selenophene, and more recently, even tellurophene are fully synthetic mimics that are incorporated with more or less efficiency into proteins via the related tryptophanyl‐ and phenylalanyl‐tRNA synthetases, respectively. In the serine/cysteine series, also selenocysteine is a proteinogenic amino acid that is inserted into proteins by a special translation mechanism, while the tellurocysteine is again most probably incorporated into proteins by the tolerance of the cysteinyl‐tRNA synthetase. For research purposes, all of these natural and synthetic chalcogen amino acids have been extensively applied in peptide and protein research to exploit their different physicochemical properties for modulating structural and functional properties in synthetic peptides and rDNA expressed proteins as discussed in the following review.

中文翻译：

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硫族元素氧，硫和硒是天然氨基酸侧链功能的重要组成部分。相反，对于较重和更金属的碲元素，迄今为止尚未发现结构和生物学功能。在甲硫氨酸系列，只有含硫蛋氨酸是一种蛋白氨基酸，而硒代甲硫氨酸和碲是被因为methionyl-的公差的并入蛋白质最可能的天然氨基酸吨RNA合成酶；迄今为止，尚未在天然化合物中发现氧类似物蛋氨酸。同样，色氨酸和苯丙氨酸的硫族元素类似物，其中苯环已被大部分等排的噻吩，硒烯取代，最近，甚至碲烯都是完全合成的模拟物，通过相关的色氨酸或多或少地有效地掺入了蛋白质中。和苯丙氨酰t RNA合成。在丝氨酸/半胱氨酸系列，也硒代半胱氨酸是由特殊的平移机构插入到蛋白质蛋白氨基酸，而tellurocysteine是再次最可能是由胱氨酰的公差并入蛋白质吨RNA合成酶。出于研究目的，所有这些天然和合成硫属元素氨基酸已广泛应用于肽和蛋白质研究，以利用它们的不同理化特性来调节合成肽和r DNA表达的蛋白的结构和功能特性，如下文所述。