Disulfide peptide

Gorman, J.J. Feiguson, B.L. Nguyen, T.B. Use of 2,6-Dihydroxyacetophenone for Analysis of Fragile Peptides, Disulfide Bonding and Small Proteins by MALDI. Rapid Commun. Mass Spectrom. 1996, 70, 529-536. 

The antibodies are similar in structure to other globulin proteins which are present in serum of vertebrates [9], The antibody molecule consists of two light polypeptide chains and two heavy polypeptide chains [10]. The amino acids are present in all the chains but the number of residues and the sequence will vary in different antibody multiforms [9], Light chains contain approximately 220 amino add residues and heavy chains about 450 residues. The complete sequence of the chains of human IgG myeloma protein has been determined by Edelman [11], The chains are held together in the unique conformational structure of the antibody molecule by a few covalent disulfide bonds between the chains and many electrostatic bonds between the amino groups of one chain and the hydroxyl groups of another chain. The covalent bonds are represented in Formula 1, 2 and 3 [peptide, disulfide and... 

The peculiar viscoelastic properties of wheat dough are the result of the presence of a three-dimensional network of gluten proteins. The network is formed by thiol-disulfide exchange reactions among gluten proteins. Peptide disulfides can interfere in a thiol-disulfide exchange system by reacting with a protein (PR)-thiol to liberate a peptide (R)-thiol and form a mixed disulfide, as follows ... 

Cleavage of disulfide bonds occurs before hydrolysis of the protein into peptides. Disulfide bonds may be cleaved oxidatively, or they may be reduced and alkylated. Treatment of the native protein with performic acid, a powerful oxidizing agent, breaks disulfide bonds and converts cystine residues to cysteic acid (Figure 3-11). Reduction of the disulfide linkage by thiols, such as d-mercaptoethanol, yields reactive sulfhydryl groups. These groups may be stabilized by alkylation with iodoacetate or ethyleneimine to yield the carboxymethyl or aminoethyl derivative, respectively. 

Figure 5.22 N-acetylglucosamine-peptide disulfide selected from a disulfide DCL targeting wheat germ agglutinin.

MS analyses revealed the amplification of an N-acetylglucosamine-peptide disulfide (Figure 5.22), as expected for this protein. 

The redox-active ferrocenoyl moieties are surrounding a central H-bonded peptide core. Fcl is involved in the square helix having a right-handed twist, as observed in most p sheets, and Fc2 is involved in the twisted helix. Both helices have a pitch height of 14A. The square helix and twisted helix have an inner diameter of 3.8 A and 4.1 A, respectively. Although peptide-disulfides often exhibit unusual structural features, a supramolecular assembly as exhibited by Fc-glycylcystamine was never before observed in peptide conjugates. 

Reduction. Raney Nickel treatment of thioacetals is a standard method for carbony 1-to-methylene reduction." In the presence of Triethylamine, (1) reduces azides to primary amines (eq 14). Under the acidic conditions employed for thioacetal formation, this reduction does not occur (eq 8). " Reduction of peptidic disulfides to dithiols can be conveniendy accomplished with (1). ... 

The second application of the CFTI approach described here involves calculations of the free energy differences between conformers of the linear form of the opioid pentapeptide DPDPE in aqueous solution [9, 10]. DPDPE (Tyr-D-Pen-Gly-Phe-D-Pen, where D-Pen is the D isomer of /3,/3-dimethylcysteine) and other opioids are an interesting class of biologically active peptides which exhibit a strong correlation between conformation and affinity and selectivity for different receptors. The cyclic form of DPDPE contains a disulfide bond constraint, and is a highly specific S opioid [llj. Our simulations provide information on the cost of pre-organizing the linear peptide from its stable solution structure to a cyclic-like precursor for disulfide bond formation. Such... 

The Cyc conformer represents the structure adopted by the linear peptide prior to disulfide bond formation, while the two /3-turns are representative stable structures of linear DPDPE. The free energy differences of 4.0 kcal/mol between pc and Cyc, and 6.3 kcal/mol between pE and Cyc, reflect the cost of pre-organizing the linear peptide into a conformation conducive for disulfide bond formation. Such a conformational change is a pre-requisite for the chemical reaction of S-S bond formation to proceed. 

Y. Wang and K. Kuczera. Conformational free energy surface of the linear DPDPE peptide Cost of pre-organization for disulfide bond formation. J. Am. Chem. Soc., submitted, 1997. 

Y. Wang and K. Kuczera. Molecular dynamics simulations of cyclic and linear DPDPE Influence of the disulfide bond on peptide fiexibility. J. Phys. Chem., 100 2555-2563, 1996. 

There are several levels of pepfide sfrucfure The primary structure is the ammo acid sequence plus any disulfide links With the 20 ammo acids of Table 27 1 as building blocks 20 dipeptides 20 tripeptides 20" tetrapeptides and so on are possible Given a peptide of unknown structure how do we determine its ammo acid sequence" ... 

The primary structure of a peptide is given by its ammo acid sequence plus any disulfide bonds between two cysteine residues The primary structure is determined by a systematic approach m which the protein is cleaved to smaller fragments even individual ammo acids The smaller fragments are sequenced and the mam sequence deduced by finding regions of overlap among the smaller peptides... 

Disulfide bridge (Section 27 7) An S—S bond between the sulfur atoms of two cysteine residues in a peptide or pro tein... 

Properties and Structure. a -Acid glycoprotein (a -AGP) has a molecular mass of about 41,000 and consists of a peptide chain having 181 amino acid residues and five carbohydrate units (14,15). Two cystine disulfide cross-linkages connect residues 5 and 147 and residues 72 and 164. The carbohydrate units comprise 45% of the molecule and contain siaUc acid, hexosamine, and neutral hexoses. In phosphate buffer the isoelectric point of the... 

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