BACKGROUND: AB INITIO CALCULATION ON PEPTIDE STRUCTURES HAS BEEN DONE [1]. BY OBSERVING RELEVANT DIHEDRAL ANGLES IN THE OPTIMIZED STRUCTURES OF SMALL AMINO ACID SEQUENCES, IT CAN BE DETERMINED IF SUCH PLANARITY IS ACTUALLY EXPECTED. THE USE OF Y 'S AND F 'S AS THE ONLY RELEVANT PARAMETERS TO CONSIDER IN PROTEIN STRUCTURE PREDICTIONS IS ALSO CONTINGENT ON THE GEOMETRY OF EACH A -CARBON. WHILE IT IS NOT EXPECTED THAT THE A -CARBON WILL HAVE PERFECT TETRAHEDRAL GEOMETRY DUE TO THE FACT THAT IT IS STEREOGENIC, IT IS ASSUMED THAT ITS BOND ANGLES THROUGHOUT EACH AMINO ACID IN A SEQUENCE SHOULD BE SIMILAR.METHODS: THE EIGHT DIPEPTIDE STRUCTURES STUDIED IN THIS PAPER WERE OPTIMIZED BOTH AT HF AND DFT LEVEL INDIVIDUALLY. OPTIMIZED ENERGY VALUES ARE OBTAINED WITH 6-311++G** BASIS SET IN EACH CASE. ALL THE COMPUTATIONS HAVE BEEN DONE USING GAUSSIAN 09 PROGROM.RESULTS: BOND ANGLE AROUND CARBON ATOM IS 109.5. BUT DUE TO THE STREOGENIC NATURE OF A-C ATOM THE IDEAL NATURE IS NOT EXPECTED. THE COMPARISON BETWEEN A-CARBON BOND ANGLES WHEN TWO HITIDINES ARE PRESENT SHOWS INTERESTING FACTS. THIS REVEALS THAT A-CARBON BOND ANGLES ARE DIFFERENT THOUGH IN BOTH SIDE HISTIDINE RESIDUES ARE PRESENT. THIS DIFFERENCE CAN BE EXPLAINED BY THE FACT THAT THE AMINE AND THE CARBOXYL ENVIRONMENT OF BOTH THE FIRST AMINO ACID AND THE X-AMINO ACID ARE DIFFERENT. DIHEDRAL ANGLE OF THE DIPEPTIDE BOND CAN GIVE SOME INFORMATION IN THIS REGARD. THE DIHEDRAL ANGLE D (DIHEDRAL ANGLE) SHOULD BE 180 IF THE AMIDE PLANE IS PLANAR.CONCLUSION: DIHEDRAL ANGLE OF THE DIPEPTIDE BOND CAN GIVE SOME INFORMATION IN THIS REGARD. AFTER A THOROUGH STUDY WITH DIFFERENT HIS-X COMBINATION WE CONCLUDE THAT HYDROGEN BONDING 19H AND OXYGEN 27O OF CARBOXYLIC ACID TERMINUS OF DIPEPTIDE PLAYS THE MAJER ROLE FOR DETERMINING THE VALUES OF D. THE INTERATOMIC DISTANCES (BETWEEN O AND H) ARE COMPATIDLE TO WEAK HYDROGEN BONDING IN PEPTIDE SYSTEMS.

RECENTLY RESEARCHERS HAVE INTERESTED IN THE NONLINEAR OPTICAL (NLO) CRYSTALS BECAUSE OF THEIR APPLICATIONS SUCH AS HIGH-SPEED INFORMATION PROCESSING, OPTICAL COMMUNICATIONS, AND OPTICAL DATA STORAGE [1-3]. AMINO ACIDS ARE SUITABLE FOR NLO APPLICATIONS...

IN THIS WORK, ADSORPTION OF HISTIDINE AMINO ACID ON THE AL12N12NANOCAGE WAS STUDIED USING DENSITY FUNCTIONAL THEORY (DFT). THE MOST STABLE ADSORBED CONFIGURATION IS HAPPENED THROUGHOUT INTERACTION OF NITROGEN ATOM OF AMINO GROUP OF HISTIDINE WITH AL ATOM OF THE NANOCAGE. ...

BACKGROUND: IN THE LAST TWO DECADES, POLYMERIC MICELLES HAVE ATTRACTED CONSIDERABLE INTEREST ESPECIALLY FOR DELIVERING ANTITUMOR DRUGS TO SOLID TUMORS, WHICH COULD BE SELF-ASSEMBLED FROM AMPHIPHILIC GRAFT COPOLYMERS. MATERIAL USED FOR THIS MICELLE SHOULD BE BIOCOMPATIBLE. AMONG POLYMERS USED IN THIS APPLICATION, POLYSACCHARIDE ATTRACT MANY ATTENTION BECAUSE OF THEIR BIOCOMPATIBILITY, BIODEGRADABILITY, CELL SURFACE RECOGNITION SITES [1] AND A LARGE NUMBER OF REACTIVE GROUPS ON THEIR STRUCTURE WHICH SIMPLIFIES TO MODIFY THE STRUCTURE TO CREATE DESIRED PROPERTIES. IN THIS STUDY DEXTRAN (DEX) WAS CHOSEN AS A HYDROPHILIC BACKBONE DUE TO ALL PROPERTIES NOTICED FOR POLYSACCHARIDE AND HAD ALREADY BEEN USED IN CLINICAL APPLICATIONS. MOREOVER, DUE TO THE 5% BRANCHING STRUCTURE AS WELL AS PLENTIFUL OF HYDROXYL GROUPS ON THE CHAINS, DEXTRAN CAN EASILY BE CHEMICALLY MODIFIED [2]. IN THIS CONTRIBUTION, BOC-HISTIDINE-GRAFTED DEXTRAN (DEX-HIS) WAS SYNTHESIZED VIA AN ESTERIFICATION REACTION. CRITICAL MICELLE CONCENTRATION (CMC) IS AN IMPORTANT CHARACTERISTIC FOR AMPHIPHILIC MATERIALS WAS DETERMINED FOR MICELLE FORMATION ABILITY...

IN THIS PAPER, A SIMPLE AND A SELECTIVE COLORIMETRIC METHOD FOR THE NAKED-EYE DETECTION ANDDETERMINATION OF HISTIDINE (HIS) IN BIOLOGICAL FLUIDS USING MUREXIDE AS AN INDICATOR AND CU2+ A RECEPTORCHEMOSENSOR IS DESCRIBED. ...