Amino acids structure-activity relationships

The rate of acid-catalyzed degradation of the penicillins also depends largely on the nature of their acylamido side chain. Structure-activity-relationship studies undertaken for the rational design of orally active penicillins have shown that the stability in gastric juice increases with the sum of Taft s inductive substituent constants (of values) of the 6-amino side chain [95]. 

Figure 1 Cartoon representation of the human cathelicidin hCAPI 8. The amino acid residues that define each of the three hCAP18 domains have been added. The sequence of LL-37, the host defense peptide derived from hCAP18, is found in the inset. Structure-activity relationship studies have identified regions within the peptide that are necessary for both antimicrobial and immunomodulatory activities.

Shen, M., Letiran, A., Xiao, Y., Golbraikh, A., Kohn, H., Tropsha, A. Quantitative structure-activity relationship analysis of functionalized amino acid anticonvulsant agents using k nearest neighbor and simulated annealing PLS methods./. Med. Chem. 2002, 45, 2811-2823. 

Structure-Activity Correlations. This detailed knowledge of the three-dimensional structure of insulin led to the recognition that its biological activity resides in an area of the molecule rather than in specific amino acid residues, just as dimerization and further association of the molecule also depend on an intact spatial structure. The foregoing concept is corroborated by structural modifications of the hormone. The last three amino acids of the B chain can be removed without a loss of activity, but cleavage of the C-terminal of the A chain (Asn ) results in a total loss of activity. Amino acids can be replaced inside the chains only if such substitution does not change the overall geometry of the molecule. The structure-activity relationships of insulin derivatives are inconsistent and not always comparable. 

Amino-acid abbreviations are spelled out in Appendix V. Through a series of structure-activity relationship studies, the bioactive conformation and peptide sequences that produce undesirable biologic responses were identihed. Also identified were sequences susceptible to proteolysis, and a working-model compound that eliminated these sequences was proposed (Figure 4.6). This allowed the rational design of optimized somatostatin analogues with desirable biologic characteristics and activity and increased stability. 

Li, Y. W., Li, B., He, J., and Qian, P. (2011). Structure-activity relationship study of antiox-idative peptides by QSAR modeling The amino acid next to C-terminus affects the activity. ]. Pept. Sci. 17, 454-462. 

For OBOC small peptide libraries or libraries with a fixed position, it is not always necessary to sequence individual beads. In cases in which structural consensus can be expected, it is sometimes much faster to sequence a multiplicity of beads. From the sequencing data, the information about the structure-activity relationships can be obtained. In the cycles with a requirement for high specificity only one particular amino acid can be found, while... 

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