a backbone chain is a long chain of amino acids linked by peptide bonds.
a backbone chain is a long chain of amino acids linked by peptide bonds.
a long chain of amino acids linked by peptide bonds is a?
backbone chain
the chemical structure of proteins was still under debate at that time. the most accepted (and ultimately correct) hypothesis was that proteins are linear polypeptides, i.e., unbranched polymers of amino acids linked by peptide bonds. however, a typical protein is remarkably long—hundreds of amino-acid residues—and several distinguished scientists were unsure whether such long, linear macromolecules could be stable in solution. further doubts about the polypeptide nature of proteins arose because some enzymes were observed to cleave proteins but not peptides, whereas other enzymes cleave peptides but not folded proteins. attempts to synthesize proteins in the test tube were unsuccessful, mainly due to the chirality of amino acids; naturally occurring proteins are composed of only "left-handed" amino acids. hence, alternative chemical models of proteins were considered, such as the diketopiperazine hypothesis of emil abderhalden. however, no alternative model had yet explained why proteins yield only amino acids and peptides upon hydrolysis and proteolysis. as clarified by linderstrøm-lang, these proteolysis data showed that denatured proteins were polypeptides, but no data had yet been obtained about the structure of folded proteins; thus, denaturation could involve a chemical change that converted folded proteins into polypeptides.
cyclol
"peptides and proteins" are oligomers or polycondensates of amino acids linked together by a carboxamide group. the threshold between the two is as at about 50 amino acids. because of their unique biological functions, a significant and growing part of new drug discovery and development is focused on this class of biomolecules. their biological functions are determined by the exact arrangement or sequence of different amino acids in their makeup. for the synthesis of peptides, four categories of fine chemicals, commonly referred to as peptide building blocks (pbbs), are key, namely amino acids (=starting materials), protected amino acids, peptide fragments and peptides themselves. along the way, the molecular weights increase from about 10 up to 10 and the unit prices from about $100 up to $10 per kilogram. however, only a small part of the total amino acid production is used for peptide synthesis. in fact, l-glutamic acid, d, l-methionine, l-aspartic acid and l-phenylalanine are used in large quantities as food and feed additives. about 50 peptide drugs are commercialized. the number of amino acids that make up a specific peptide varies widely. at the low end are the dipeptides. the most important drugs with a dipeptide (l-alanyl-l-proline) moiety are the “-pril” cardiovascular drugs, such as alapril (lisinopril), captoril (captopril), novolac (imidapril) and renitec (enalapril). also the artificial sweetener aspartame (n-l-α-aspartyl-l-phenylalanine 1-methyl ester) is a dipeptide. at the high end there is the anticoagulant hirudin, mw ≈ 7000, which is composed of 65 amino acids.
fine chemical