Tadamichi Hirabayashi

Accelerated biodegradation of poly(vinyl alcohol) by a glycosidation of the hydroxyl groups

Abstract Biodegradability of N-acetyl- d -glucosamine (GlcNAc)-substituted poly(vinyl alcohol) (PVA) (1) in a soil suspension (pH 6.5) was investigated at 25°C for 40 days. Biochemical oxygen demand (BOD) of 1 with degree of substitution of 0.2–0.3 (DP=430–480) was higher than that of PVA under the degradation condition. Size exclusion chromatography (SEC), 1H NMR, and FT-IR measurements of the recovered sample indicated that biodegradation of PVA main chain was accelerated by partial glycosidation of hydroxyl groups in PVA.

Terminal effect of chiral residue on helical screw sense in achiral peptides

To understand the terminal effect of chiral residue for determining a helical screw sense, we adopted five kinds of peptides I–V containing N- and/or C-terminal chiral Leu residue(s): Boc–L-Leu–(Aib–ΔPhe)2–Aib–OMe (I), Boc–(Aib–ΔPhe)2–L-Leu–OMe (II), Boc–L-Leu–(Aib–ΔPhe)2–L-Leu–OMe (III), Boc–D-Leu–(Aib–ΔPhe)2–L-Leu–OMe (IV), and Boc–D-Leu–(Aib–ΔPhe)2–Aib–OMe (V). The segment –(Aib–ΔPhe)2– was used for a backbone composed of two “enantiomeric” (left-/right-handed) helices. Actually, this could be confirmed by 1H-nmr [nuclear Overhauser effect (NOE) and solvent accessibility of NH resonances] and CD spectroscopy on Boc–(Aib–ΔPhe)2–Aib–OMe, which took a left-/right-handed 310-helix. Peptides I–V were also found to take 310-type helical conformations in CDCl3, from difference NOE measurement and solvent accessibility of NH resonances. Chloroform, acetonitrile, methanol, and tetrahydrofuran were used for CD measurement. The CD spectra of peptides I–III in all solvents showed marked exciton couplets with a positive peak at longer wavelengths, indicating that their main chains prefer a left-handed screw sense over a right-handed one. Peptide V in all solvents showed exciton couplets with a negative peak at longer wavelengths, indicating it prefers a right-handed screw sense. Peptide IV in chloroform showed a nonsplit type CD pattern having only a small negative signal around 280 nm, meaning that left- and right-handed helices should exist with almost the same content. In the other solvents, peptide IV showed exciton couplets with a negative peak at longer wavelengths, corresponding to a right-handed screw sense. From conformational energy calculation and the above 1H-nmr studies, an N- or C-terminal L-Leu residue in the lowest energy left-handed 310-helical conformation was found to take an irregular conformation that deviates from a left-handed helix. The positional effect of the L-residue on helical screw sense was discussed based on CD data of peptides I–V and of Boc–(L-Leu–ΔPhe)n–L-Leu–OMe (n = 2 and 3).

NEW MEASUREMENT OF HYDROGEN GAS AND ACETONE VAPOR IN GASES EMANATING FROM HUMAN SKIN

ABSTRACT We have found that hydrogen gas and acetone vapor emanate from human skin. Emanation gases from human skin were collected for 5–10 min from arm, palm, or forefinger with a homemade probe and bags. The trapped gases were analyzed by gas chromatography, and hydrogen gas and acetone vapor were found to exist in all subjects. The probe (44 mm outer diameter, 6 mm height and inner volume of 3.8 mL) directly covered a 9.4 cm2—flat skin surface of the arm, and a modified Tedlar bag or aluminum bag could cover a finger or the whole palm. The average rates of acetone vapor and hydrogen gas released from human skin (15 subjects) is 80–800 and 5–50 pg cm−2 min−1, respectively. There is a good linear relationship between the emanation rate and the concentration of those gases in human breath. Correlation factors for acetone vapor and hydrogen gas are 0.81 and 0.66, respectively. The proposed non-invasive clinical technique imposes only very minor physical stress on a subject during sampling.

Chemical modification of hydroxyl groups of poly(vinyl alcohol) by a glycosidation reaction

A new procedure for chemical modification of poly(vinyl alcohol) (PVA) was established by a glycosidation reaction of hydroxyl groups in PVA with triacetylated sugar oxazoline 1. 1 H and 13 C NMR analyses indicated that triacetylated N-acetyl-D-glucosamine (GlcNAc) was introduced onto a PVA backbone selectively via a β-O-glycoside linkage. Deacetylation of triacetylated GlcNAc-substituted PVA 2 resulted in GlcNAc-substituted PVA 3 in good yield. These modified PVAs 2 and 3 exhibited solubilities and thermal properties different from the original PVA.

Equivalent cross-relaxation rate imaging in the synthetic copolymer gels and invasive ductal carcinomas of the breast

The values of equivalent cross-relaxation rate (ECR) correlated well with [i] water conditions in various copolymer gels and [ii] nature of malignant cells with regard to nuclear dysplasia and mitotic potential in breast carcinomas. The synthetic copolymer gels composed of any two or three monomers among 2-hydroxyethyl methacrylate (HEMA), glycidyl methacrylate (GMA), N-vinyl-2-pyrrolidinone (N-VP), methyl methacrylate (MMA) and benzyl methacrylate (BMA). The ECR measurement was performed by using an off-resonance saturation pulse under conventional field-echo imaging at frequency within +/- 75 ppm apart from the water resonance frequency. The ECR values were readily to determine and non-time consuming parameter for cross relaxation rate. The ECR values at the frequency offset by 7-ppm (ECR-7) were divided the sample gels two classes, which must correspond to hydrophilic or hydrophobic ones. The sensitivity in the gels was nearly equivalent to the cross-relaxation rate itself. In the breast carcinomas, the ECR-7 correlates with the nature of malignant cells with regard to nuclear dysplasia and mitotic potential. The ECR-7 is better or more accurate than the STR-7 because the SDNRs between carcinoma and glandular tissue increased by approximately 50% on the ECR-7 compared with the STR-7. Thus the ECR values could be a new parameter for malignancy and cell proliferative activity of the breast carcinomas with non-invasive modalities by magnetic resonance imaging.

Synthesis of ΔEPhe‐containing tripeptide via photoisomerization and its conformation in solution

A new synthetic route to (E)-beta-phenyl-alpha,beta-dehydroalanine (delta(E)Phe)-containing peptide was presented via photochemical isomerization of the corresponding (Z)-beta-phenyl-alpha,beta-dehydroalanine (delta(Z)Phe)-containing peptide. By applying this method to Boc-Ala-delta(Z)Phe-Val-OMe (Z-I: Boc, t-butoxycarbonyl; OMe, methoxy), Boc-Ala-delta(E)Phe-Val-OMe (E-I) was obtained. The identification of peptide E-I was evidenced by 1H-nmr, 13C-nmr, and uv absorption spectroscopy, elemental analysis, and hydrogenation. The conformation of peptide E-I in CDCl3 was investigated by 1H-nmr spectroscopy (solvent dependence of NH chemical shift and difference nuclear Overhauser effect). Interestingly, peptide E-I differed from peptide Z-I in the hydrogen-bonding mode. Namely, for peptide Z-I, only Val NH participates in intramolecular hydrogen bonding, which leads to a type II beta-turn conformation supported by hydrogen bonding between CO(Boc) and NH(Val). On the other hand, for peptide E-I, two NHs, delta(E)Phe NH and Val NH, participate in intramolecular hydrogen bonding. In both peptides, a remarkable NOE (approximately 11-13%) was observed for Ala C(alpha) H-deltaPhe NH pair. Based on the nmr data and conformational energy calculation, it should be concluded that peptide E-I takes two consecutive gamma-turn conformations supported by hydrogen bonding between CO(Boc) and NH(delta(E)Phe), and between CO(Ala) and NH(Val) as its plausible conformation.

Is endogenous isoprene the only coeluting compound in the measurement of breath pentane

Pentane is a widely used index of lipid peroxidation. Although isopentane, an isomer of pentane, is a major component of ambient air in urban areas, many studies have disregarded the possibility that this compound is coeluted in the measurement of breath pentane. In the present study, a gas chromatograph equipped with a cold trap apparatus and a large-bore glass capillary column was used for determination of pentane, isopentane and isoprene in breath and ambient air. Isoprene was detected in all subjects at a concentration higher than that in the ambient air. However, the concentrations of breath pentane and isopentane were similar to, or less than, those of the ambient air. We suggest that great care is required in the measurement of breath pentane so that endogenous isoprene and ambient isopentane are not coeluted.

Insertion reactions of diethylaluminum derivatives : X. Synthesis and properties of ethylaluminum sulfide, the initial product in the reaction of triethylaluminum with hydrogen sulfide

Abstract Ethylaluminum sulfide, (EtAls) n , was found to be the initial product of the reaction of triethylaluminum with hydrogen sulfide. When heated with an equimolar amount of triethylaluminum, this sulfide gave bis(diethylaluminum) sulfide, (Et 2 Al) 2 S. (EtAls) n reacted with pyridine or vinylpyridines to form (EtAls) 2 · 2(Donor) type adducts and N,N -dimethylamides, RCONMe 2 (R = H, Me, Ph), to give the corresponding thioamides in good yield.

Structural and conformational properties of (Z)-?-(1-naphthyl)- dehydroalanine residue

To understand how chemical structure of beta-substituted alpha, beta-dehydroalanine (particularly size and pi conjugation of beta substituent) affects conformational property, x-ray crystallographic analysis was performed on Boc-Ala-Delta(Z) Nap-Val-OMe [Boc: t-butoxycarbonyl; Delta(Z) Nap: (Z)-beta-(1-naphthyl)dehydroalanine; OMe: methoxy] having the naphthyl group as a bulky beta substituent. Single crystals were grown by slow evaporation from an ethanol solution in the triclinic space group P1 with a = 9.528 (3) A, b = 12.410(4) A, c = 5.975(2) A, alpha = 96.77(3) degrees, beta = 102. 81(2) degrees, gamma = 88.74(3) degrees, V = 684.1(4) A3, and Z = 1. Phase determination was carried out by a direct method (SHELEXS), and the final structure was refined to R = 8.1% and R(w) = 9.0% for 1964 observed reflections. The bond lengths and bond angles of the Delta(Z)Nap residue, characterized by a sp(2) hybridized C(alpha) atom, did not differ from those of other dehydroresidues such as Delta(Z) Phe, Delta(Z) Leu, and DeltaVal essentially. The peptide backbone took a type II beta-turn conformation involving an intramolecular hydrogen bond between CO(Boc) and NH(Val), similar to di- or tripeptides containing a Delta(Z) Phe or Delta(Z) Leu residue in the second positions. Here the naphthyl group was found to be nonplanar [chi(2) = 55(1) degrees ] relative to the C(alpha)==C(beta)==C(gamma) plane. The nonplanarity was supported by conformational energy calculation. The molecular packing was stabilized by two kinds of intermolecular hydrogen bonds and van der Waals interactions. Naphthyl groups were arranged in a partially overlapped face-to-face orientation with a center-to-center distance of 5.97 A. For additional information, peptide Boc-(Ala-Delta(Z) Nap-Leu)(2)-OMe was synthesized and its solution conformation was investigated by (1)H-NMR spectroscopy. The hexapeptide showed the tendency to form a 3(10)-helical conformation in solution essentially. Conformational properties of Delta(Z) Nap residue, characterized by a type II beta-turn and 3(10)-helix, were supported by a conformational energy contour map of the Delta(Z)Nap residue.

A helical arrangement of β‐substituents of dehydropeptides: Synthesis and conformational study of sequential nona‐ and dodecapeptides possessing (Z)‐β‐(1‐naphthyl)dehydroalanine residues

Sequential nona- and dodecapeptides possessing three and four (Z)-beta -(1-naphthyl)dehydroalanine (Delta(Z)Nap) residues, Boc-(L-Ala-Delta(Z)Nap-L-Leu)(n)-OCH(3) (n = 3 and 4; Boc = t-butoxycarbonyl), were synthesized to design a rigid 3(10)-helical backbone for a regular arrangement of functional groups using dehydropeptides. Their solution conformations were investigated by NMR and CD analyses, and theoretical energy calculations. Both peptides were found to adopt a 3(10)-helical conformation in CDCl(3) from their nuclear Overhauser effect spectroscopy (NOESY) spectra, which showed intense cross peaks for N(i)H-N(i+1)H proton pairs, but no cross peaks for C(alpha)(i)H-N(i+4)H pairs. The predominance of a 3(10)-helix was also supported by solvent accessibility of NH resonances. CD spectra of both peptides in tetrahydrofuran showed strong exciton couplets at around 228 nm assignable to naphthyl side chains, which are regularly arranged along a right-handed helical backbone. Chain-length effects on conformational preference in sequential peptide -(Ala-Delta(Z)Nap-Leu)(n)- were discussed based on spectroscopic analysis, energy minimization, and molecular dynamics simulations. Consequently, the repeating number n > or = 3 forms predominantly a right-handed 3(10)-helical conformation. The energy calculation also revealed that the midpoint naphthyl groups of peptide n = 4 are highly restricted to one stable orientation. In conclusion, beta-substituted alpha,beta-dehydroalanine is expected to be a unique tool for designing a rigid molecular frame of 3(10)-helix along which beta-functional groups are regularly arranged in a specific manner.