Search

A new procedure is described for sequencing of peptide mixtures by a combination of Edman degradation and field-desorption mass spectrometry. The procedure involves measurement of the mass values of quasi-molecular ions ([M + H]+) of constituent peptides in the mixture and their fragments degraded by the Edman method. Calculation of all the possible mass differences of the mass values before and after degradation and identification of the phenylthiohydantoins released reveal the N-terminal amino acids of individual peptides in the mixture. Repetition of these operations gives the amino acid sequences of individual peptides in the mixture. As typical examples, the sequencing of peptide mixtures prepared by proteolytic digestion of glucagon are described. In addition, a computer program was designed for determining the possible sequences of proteins from the partial sequences and mass values of their proteolytic peptides. Output data showed that the entire amino acid sequence of glucagon can be determined by only four and two cycles of degradation of chymotryptic and tryptic peptides, respectively.

In this paper the synthesis of the following elongated tuftsin analogs: Arg-Thr-Lys-Pro-Arg (1), Pro-Arg-Thr-Lys-Pro-Arg(II), Lys-Pro-Arg-Thr-Lys-Pro-Arg(III) and Thr-Lys-Pro-Arg-Thr-Lys-Pro-Arg(IV) by classical and solid-phase methods are described. The obtained peptides were tested for their biological activity: restoration of the phagocytosis of defected granulocytes from blood of children with acute lymphoblastic leukemia (ALL).

IR spectra of ten tuftsin structural analogues containing D-amino acid residues were investigated in solid state, and in chloroform and carbon tetrachloride solutions. The effect of configurational changes on folding ability of the peptide and on formation of beta-bend structure seems to depend on the position of the altered residue.

Normal host defense against microbial invaders depends upon an intact humoral and cellular system of inflammation and specific immunity. The major weapons for killing microbes that invade tissue are phagocytic cells, however, humoral factors enable these phagocytic cells to recognize, migrate toward, efficiently ingest, and kill the invaders. Humoral factors essential for host defense include specific antimicrobial immunoglobulin antibodies and multiple proteins which comprise the complement system. The complement system is the oldest phylogenetically and the most important protein in this system is C3. When C3 is activated on the surface of the microbe, ligan is formed which provides a firm bond between organisms and phagocytic cells. This process is termed opsonization and activated C3/C3b is a highly efficient opsonin. C3b attachment stimulates efficient engulfment by phagocytic cells and most microbes are rapidly killed once they are ingested. Complement may also function as a direct bactericidal factor when associated with specific antibody on the bacterial surface. Neisseria meningitidis and Neisseria gonorrheae are susceptible to this action of complement which requires participation of the terminal proteins of the system C6, 7, 8, and 9. Patients without these terminal components, therefore, are susceptible to systemic infections with Neisseria. Septicemia from Streptococcus pneumoniae and other encapsulated microbial species occurs with greatly increased frequency in patients without spleens. Complement and other as yet unidentified humoral factors which contribute to host defense against microbial invaders appear to be deficient in patients without spleens. Antimicrobial antibodies produced in response to antigenic stimulation by microbes are also essential humoral factors. Effective levels of antimicrobial antibodies develop only after microbes have colonized their host and the immune system has been stimulated and protection is delayed. Once produced, however, specific antibodies are potent opsonins and are effective activators of complement. Highly effective and efficient host defense is present when there are circulating specific antibacterial antibodies and an intact complement system. Septicemia may occur when there is a traumatic portal or entry of an exceptionally large bacterial challenge, however, deficiency of humoral or cellular factors of host defense is frequently involved in the pathogenesis of septicemia. Measures for preventing septicemia in susceptible persons include active immunization with microbial antigens or passive therapy with specific antimicrobial antibodies.

Peptidases capable of releasing proline residues from polypeptides are present in the cytoplasmic fraction of rabbit polymorphonuclear granulocytes. This was shown with peptide substrates where proline is present either at the carboxy-terminal or within the polypeptide chain. Lysosomal and plasma membrane enzymes were inactive towards such polypeptides. The proline residue was hydrolyzed at either its amino end or its carboxy end. It is noteworthy that a Pro:Pro bond was cleaved both in the pentapeptide Thr-Lys-Pro-Arg and the dipeptide Pro:Pro.

The ability of tuftsin and its analogs to form folded intramolecularly hydrogen-bonded structures has been investigated by infrared spectroscopy. The appearance of beta-turns is documented for peptides containing proline in position 3 of the chain. Correlation of spectroscopic data with biological activity in the investigated series is attempted.