Digestion of crosslinked poly(vinylpyridinium halide) by activated sludge,and application to make poly(methyl methacrylate) biodegradable by incorporation of a pyridinium group into the main chain

Crosslinked poly(N-benzyl-4-vinyipyridinium bromide) has been found to be digested by activated sludge obtained from sewage works. As an extension of this work, the authors attempted to make poly(methyl methacrylate) biodegradable by incorporation of a pyridinium group. Poly(methyl methacrylate) containing a small amount of N-benzyl-4-vinylpyridinium chloride in the main chain showed remarkable reduction in molecular weight and gravimetric weight when placed in an aeration tank of a sewage works. Molecular weight reduction by activated sludge was more conspicuous when content of the pyridinium group was larger and the original molecular weight before the biological treatment was lower. Since insoluble pyridinium-type polymer captures microbial cells alive, this biodegradation appears to be facilitated by enhancement of affinity of the synthetic hydrophobic polymer with cells of microogranisms. © 1994 John Wiley & Sons, Inc.     

The efficiency and timing of initiation of replication of multiple replicons of Saccharomyces cerevisiae chromosome VI

BACKGROUND: A complete set of nine ARSs was identified (the tenth ARS in this paper), mapped on chromosome VI of Saccharomyces cerevisiae, and characterized for functional elements. RESULTS: The level of activity of all ARSs as chromosomal replication origins was determined by neutral/neutral 2D gel-electrophoresis. These origins were classified into three groups: (i) three high frequency origins used once nearly every cell cycle, (ii) four intermediate frequency origins used once in two to three cycles and (iii) two low frequency origins used in fewer than 5% of cell cycles. These variations in initiation frequency among origins of chromosome VI are present in three common laboratory wild-type strains. Each origin is initiated at a fixed time and passively replicated by incoming replication forks at a fixed time during a synchronous S phase. Replication of each arm of the chromosome starts from one major origin located one-fifth (left arm) and one-third (right arm) of the distance from the centromere, and expands sequentially in both directions. Two telomere vicinity origins are replicated last. Time of initiation and replication of the last replicating origin, Ori609, was remarkably variable from cell to cell. CONCLUSIONS: Chromosome VI of S. cerevisiae contains nine replication origins that comprise five active replicons under normal cell growth conditions. A clear correlation was found between the efficiency of initiation and the order of replication. The timing of initiation of most origins, except for the first and last, is coincident with the time of passive replication by incoming forks from neighbouring origins.     

Biodegradability of poly(vinyl acetate) containing a pyridinium group

An attempt has been made to give biodegradability to poly(vinyl acetate) by partial modification of the chemical structure. Poly(vinyl acetate) containing a small amount of N-benzyl-4-vinylpyridinium chloride (PVAc-co-VPC) and that containing 16 mol % of methyl acrylate and a small amount of the pyridinium group (PVAc-co-MA-co-VPC) showed significant degradation when placed in an aeration tank of sewage works. Control polymers possessed of no pyridinium group did not show significant degradation under these conditions, and the extent of weight reduction during the treatment increased with the content of the pyridinium group. The weight reduction exhibited an uppermost limit after 7 days of the treatment, and the pyridinium group disappeared from the polymer during the early period. Incorporation of the pyridinium group into poly(vinyl acetate) appeared to have improved the biodegradability. Gel permeation chromatographic analysis showed that the low molecular weight fraction was more easily degraded than was the high molecular weight fraction. In the degradation of PVAc-co-MA-co-VPC, the unit of methyl acrylate was more easily removed than that of vinyl acetate. © 1995 John Wiley & Sons, Inc.     

Removal of virus from water by filtration using microporous membranes made of poly(N-benzyl-4-vinylpyridinium chloride)

Two types of microporous filter materials were developed for removing virus from water by using poly(N-benzyl-4-vinylpyridinium chloride) that captures virus in water. Conventional ultrafiltration using one to three sheets of 145-μm-thick cellulose nitrate membrane with a pore size of 0.45 μm and coated with 1.7 mg/g of poly(N-benzyl-4-vinylpyridinium chloride-co-styrene) showed 99.4–99.998% removal (2.2–4.7 log₁₀-unit reduction in concentration) of bacteriophage T4, whereas the control experiments using noncoated membrane showed 91–96% removal (1.0–1.4 log₁₀-unit reduction in concentration) of the virus. A composite 360-μm-thick microporous membrane with a pore size of 20 ¨︁m was prepared that consisted of connected minute beads of 1.7 ¨︁m in diameter made of crosslinked poly(N-benzyl-4-vinylpyridinium chloride) and reinforced by a nonwoven cloth. Simple filtration using one sheet of the composite membrane at 34.2cm/h showed 99.96–99.9995% removal (3.4–5.3 log₁₀-unit reduction in concentration). The virus was not detected in the filtrate when two sheets of the composite membrane were used. © 1996 John Wiley & Sons, Inc.     

Separation of alcohol–water mixture by pervaporation through a reinforced polyvinylpyridine membrane

A membrane consisted of cross-linked poly(4-vinylpyridine) and reinforced by a nonwoven cloth made of poly(ethylene terephthalate) was prepared by copolymerization of 4-vinylpyridine with divinylbenzene in the presence of the nonwoven cloth. Pervaporation performance of this polyvinylpyridine membrane was examined at several feed alcohol concentrations and temperatures. The membrane showed water selectivity, and the permselectivity, α_W/_A, for the alcohol–water mixture was in the order isopropyl > propyl > tert-butyl > ethyl > methyl. The membrane showed a large permeability, and the pervaporation flux, ?, for the ethanol–water mixture was 7–13 kg/h per square meter of the membrane in pervaporation with sweeping of carbon dioxide under atmospheric pressure and at 40°C. The membrane was durable and long lasting for a prolonged-period, and permselectivity and permeability of the membrane did not fall off even after repeated use for 1000 h. © 1993 John Wiley & Sons, Inc.     

Regulation of cystathionine gamma-lyase in Saccharomyces cerevisiae.

Regulation of the two enzymes in reverse trans-sulfuration was investigated in Saccharomyces cerevisiae. In wild-type strains, cystathionine gamma-lyase, but not cystathionine beta-synthase, was depressed nearly 15-fold if cells were starved for both inorganic and organic sulfur compounds. In a met17 strain which is defective of O-acetylserine and O-acetylhomoserine sulfhydrylase, the same enzyme was derepressed if organic sulfur compounds were limited; the repressive effect was in the order of glutathione greater than methionine greater than cysteine. The repressive effect of methionine was not observed, however, in a cys2 cys4 strain which is deficient of serine O-acetyltransferase and cystathionine beta-synthase, indicating that methionine itself is not the effector. The weak repressive effect of cysteine was attributed to inefficient uptake of this amino acid. Our observations indicate that cystathionine gamma-lyase is the target of regulation in reverse trans-sulfuration and that cysteine is very likely to be the effector of this regulation.