ABSTRACT
This investigation examined the reliability of the Synthetic Sentence Identification (SSI) test. An adaptive procedure was used to assess speech recognition thresholds (SRTs) for the SSI lists over two separate test sessions. The commercially available Davy Crockett passage and a multitalker babble were used as competition. Subjects consisted of 20 adults with normal hearing sensitivity. Results indicated (1) significantly higher SRTs with the multitalker babble, (2) significant differences in SRTs among SSI lists when using the Davy Crockett competition, (3) no significant learning/practice or fatigue effects across trials in either noise condition, and (4) high test-retest reliability across test sessions. Clinical implications of these data are considered.
Subject(s)
Speech Perception/physiology , Adolescent , Adult , Female , Humans , Male , Reproducibility of Results , Speech Discrimination TestsABSTRACT
3-Nitro-2-pyridinesulfenyl chloride (NpysCl) is the starting material for the synthesis of N-, O- and S-Npys-protected amino acids. Two efficient, novel synthetic routes to NpysCl are described. The stability of NpysCl was determined in a variety of solvents, with and without base, to determine the most suitable solvent and base for the synthesis of N-Npys amino acids. The syntheses of Npys-Ala and Boc-Lys(Npys) tert-butylammonium salt are also described.
Subject(s)
Pyridines/chemistry , Alanine/analogs & derivatives , Drug Stability , Lysine/analogs & derivatives , SolventsABSTRACT
Resins sold by several companies were examined for swelling, uniformity of beads, and substitution in the case of resins sold with the first amino acid attached. Effects of resin swelling, uniformity, and substitution on the solid phase synthesis of long, structured and/or branched peptides were evaluated.
Subject(s)
Peptides/chemical synthesis , Protein Structure, Secondary , Resins, Synthetic/chemistry , Amino Acid Sequence , Microspheres , Molecular Sequence DataABSTRACT
gamma-Carboxyglutamic acid (Gla) is believed to bind Ca [II] ions and Mg [II] ions in prothrombin and other coagulation proteins. Binding constants for H+, Ca [II] ions, and Mg [II] ions to Gla-containing peptides are determined using pH and ion selective electrode titrations. The binding constants for peptides containing a single Gla residue are similar to the constants for malonic acid. Peptides containing two Gla residues in sequence (di-Gla peptides) bind Ca [II] ions and Mg [II] ions more strongly. KMgL for the di-Gla peptides is similar to the site-binding constant for Ca [II] ions in denatured BF1. These di-Gla peptides may be useful analogs for metal binding by the disordered Gla domain in BF1.
Subject(s)
1-Carboxyglutamic Acid/metabolism , Calcium/metabolism , Magnesium/metabolism , Peptides/metabolism , Binding Sites , Kinetics , Malonates/metabolism , Models, Chemical , Molecular Structure , Osmolar Concentration , Peptides/chemical synthesis , Protein Binding , ProtonsABSTRACT
1,1,4,4-Butanetetracarboxylic acid (BTCA) is evaluated as an analogue for the metal binding site in dipeptides of gamma-carboxyglutamic acid (Gla). Molecular modeling suggests that the four carboxylic acid groups in BTCA can assume a similar conformation to the four gamma-carboxylic acid groups in GlaGla and thus provides the impetus for the synthesis and metal binding determinations. BTCA is synthesized via the tert.-butyl ester and characterized via NMR, mass spectroscopy, and elemental composition. Equilibrium binding constants with protons, Ca(II) and Mg(II) are determined via pH and Ca(II) ion-selective electrode titrations and are found to be similar to those for GlaGla peptides with blocked termini.
