CHMI-2227EL Lecture Notes - Lecture 4: Dipeptide, Aldehyde, Nutrasweet
27 Jun 2018
School
Course
Professor
Biochemistry - Day 4 2018.01.24.
***Characteristics of Peptide Bonds
-The atoms involved in the peptide C-N bond form a rigid planar unit
-The peptide bond has no freedom of rotation because of its partial double-bond
character
-The length of the peptide C-N bond is shorter then expected for single bonds
-The bonds involving the alpha carbon can rotate feel
-Peptide bonds are very stable
-Peptide bonds can be cleaved by proteolytic
enzymes
-By convention, peptides are written from the
left, beginning with the free -NH3+ group and
ending with the free -CO2- group
-Exampke Ser-Gly-Tyr-Ala-Leu or SGYAL
-The grey regions are the peptide bonds
-Conventionally we draw the carboxyl terminal
on the right and the amino terminal on the left,
therefore from left to right it is amino group to
caroxyl group
Writing Peptides
-In naming peptides we proceed amino acid by amino acid from the N-terminus
(amino) to the C-terminus (carboxyl)
-Names of all residues, except the C terminal one, end in “yl”, and the last one (the C
terminal) ends in its own name as is
-Example: Glycyl-phenylalanyl-leucyl-tyrosine
Reactivity of Amino Acids
-Cysteine Oxidation
-Cystine has a highly reactive sulfhydryl group
(SH), and they will both react together to form an
S-S bridge
-Oxidation of 2 molecules of cysteine form a
covalently linked dimetric amino acid called
cystine
-Cystine is a molecule that contains a disulphide
bond (disulfide bridge) or S-S bridge, as stated
above
-Disulfide bridges help stabilize many polypeptides
and proteins
find more resources at oneclass.com
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Document Summary
The atoms involved in the peptide c-n bond form a rigid planar unit. The peptide bond has no freedom of rotation because of its partial double-bond character. The length of the peptide c-n bond is shorter then expected for single bonds. The bonds involving the alpha carbon can rotate feel. Peptide bonds can be cleaved by proteolytic enzymes. By convention, peptides are written from the left, beginning with the free -nh3+ group and ending with the free -co2- group. The grey regions are the peptide bonds. Conventionally we draw the carboxyl terminal on the right and the amino terminal on the left, therefore from left to right it is amino group to caroxyl group. In naming peptides we proceed amino acid by amino acid from the n-terminus (amino) to the c-terminus (carboxyl) Names of all residues, except the c terminal one, end in yl , and the last one (the c terminal) ends in its own name as is.
