Cross-checking of nanoelectrospray ionization mass spectrometry and computer simulation for the evaluation of the interaction strength of non-covalently bound enkephalins in solution

Nanoelectrospray ionization mass spectrometry (nanoESI-MS) and computer simulation were applied to the characterization of non-covalent interactions of [Leu5]-enkephalin (LE) and its optical isomers, [D-Tyr1, Leu5]-enkephalin (Y-LE), [D-Phe4, Leu5]-enkephalin (F-LE) and [D-Tyr1, D-Phe4, Leu5]-enkephalin (YF-LE). The dimer formation tendencies of the optical isomers of LE were evaluated by nanoESI-MS using quadruply deuterated LE (H2N-Tyr-(2,2-d2)Gly-(2,2-d2)Gly-Phe-Leu-COOH, d4-LE) as an internal standard. The relative interaction strengths of the optical isomers of LE were estimated to be Y-LE < F-LE < LE < YF-LE. Geometry optimization calculations were performed for interactions in vacuo and in water using a semi-empirical SCF method (PM3). The initial coordinate of the dimer structure of LE was taken from that obtained from single-crystalline x-ray diffraction analysis. Estimates of the interaction strengths of the dimer complexes were based on the heats of formation of a dimer complex (Hd) and the corresponding monomers (Hm) using the equation DeltaH = Hd - 2Hm. The values of DeltaH obtained from the calculations for interactions in water decreased in the order Y-LE > F-LE > LE > YF-LE. Since the smaller values of DeltaH correspond to stronger interactions between peptides, the results from computer simulations were qualitatively consistent with those obtained from the nanoESI experiments. The possibility of cross-checking these independent techniques was demonstrated using medium-sized molecules of biological importance. The agreement of the results from the two techniques suggested that nanoESI experiments, at least qualitatively, reflected the relative interaction strengths of non-covalently bound enkephalins in aqueous solution.     

Preparation of adsorbents for affinity chromatography using TSKgel Tresyl-Toyopearl 650M

The optimum conditions for the coupling of proteins were investigated using TSKgel Tresyl-Toyopearl 650M. They were dependent on the proteins coupled. For example, when soybean trypsin inhibitor was coupled at pH 8 the coupling was completed within 1 h and the subsequent adsorption capacity for trypsin was maximal. Longer coupling times decreased the adsorption capacity due to multi-point attachment. The adsorbents obtained were successfully used for affinity chromatography in a short time.     

Analysis of waterborne paints by gas chromatography-mass spectrometry with a temperature-programmable pyrolyzer

Gas chromatography-mass spectrometry (GC-MS) with a temperature-programmable pyrolyzer was used for the analysis of waterborne paints. Evolved gas analysis (EGA) profiles of the waterborne paints were obtained by this temperature-programmed pyrolysis directly coupled with MS via a deactivated metal capillary tube. The EGA profile suggested the optimal thermal desorption conditions for solvents and additives and the subsequent optimal pyrolysis temperature for the remaining polymeric material. Polymers were identified from pyrograms with the assistance of a new polymer library. The solvents were identified from the electron ionization mass spectra with the corresponding chemical ionization mass spectra. The additive was identified as zinc pyrithione by comparison with authentic standard. Zinc pyrithione cannot be analyzed by GC-MS as it is. However, the thermal decomposition products of zinc pyrithione could be detected. The information on the decomposition temperature and products was useful for the identification of the original compound.     

Deoxygenation of sugar trifluoromethanesulfonates by sodium metal in liquid ammonia and by photolysis

Several trifluoromethanesulfonyl(TFMS) derivatives of sugars were prepared and treated with sodium in liquid ammonia or subjected to ultraviolet irradiation. Three 3-$\text{O}$-TFMS derivatives gave the corresponding 3-deoxy compounds, but a 2-$\text{O}$-TFMS derivative gave a branched-chain sugar.     

Catalytic asymmetric synthesis of alpha-amino phosphonates using enantioselective carbon-carbon bond-forming reactions

We have developed highly enantioselelctive reactions of silicon enolates with N-acyl-alpha-iminophosphonates leading to optically active alpha-amino phophonates. A copper (II)-diamine complex was shown to be effective in this reaction, and high levels of yield and selectivity were achieved. It is noteworthy that this reaction opens a way to various biologically important, optically active alpha-amino phosphonate derivatives.     

Ab initio SCF study of the interaction between L-serine phosphate and ammonia

The possible conformational changes of L -serine phosphate due to the interaction with ammonia are investigated by means of ab initio MO-LCAO-SCF calculations, using a supermolecule approach and an STO -3G basis set. The most favorable conformation of a four-hydrated L -serine phosphate anion is found to be changed by the binding of an ammonium ion. Cointeraction of ammonia and NH suggests another conformational change through the displacement of the bridging water molecule of the polyhydrated L -serine phosphate anion.     

Synthesis of Latia luciferin benzoate analogues and their bioluminescent activity

The bioluminescent system of the univalve shell Latia neritoides exhibits a luciferin-luciferase reaction. We study the enol formate structure of Latia luciferin, which is expected to be important for luminescent activity. The Latia luciferin analogues with an enol substituted benzoate moiety were synthesized and their bioluminescent activity was measured. The Latia luciferin benzoate analogues delay emission for natural luciferin in bioluminescence, indicating that the Latia bioluminescent activity can be controlled by the design of the enol ester.     

Synthesis and photovoltaic properties of thieno[3,4‐b]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2‐d]imidazole‐containing conjugated polymers

Novel conjugated polymers composed of benzo[1,2‐b:4,5‐b′]dithiophene and thieno[3,4‐b]pyrazine or dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2‐d]imidazole units are synthesized by Stille polycondensation. The resulting polymers display a longer wavelength absorption and well‐defined redox activities. The effective intramolecular charge‐transfer and energy levels of all polymers are elucidated by computational calculations. Bulk‐heterojunction solar cells based on these polymers as p‐type semiconductors and [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM) as an n‐type semiconductor are fabricated, and their photovoltaic performances are for the first time evaluated. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1067–1075