Sim2, a basic helix-loop-helix (bHLH)-PAS transcriptional repressor, is thought to be involved in some symptoms of Down's syndrome. In the course of searching for hypothetical Sim2 relatives, we isolated another bHLH-PAS factor, NXF. NXF was a novel gene and was selectively expressed in neuronal tissues. While no striking homolog of NXF was found in vertebrates, a Caenorhabditis elegans putative transcription factor, C15C8.2, showed similarity in the bHLH-PAS domain. NXF had an activation domain as a transcription activator, and Arnt-type bHLH-PAS subfamily members were identified as the heterodimer partners of NXF. The NXF/Arnt heterodimer was capable of binding and activating a subset of Sim2/Arnt target DNA variants, and Sim2 could compete with the NXF activity on the elements. We showed that Drebrin had several such NXF/Arnt binding elements on the promoter, which could be direct or indirect cross talking points between NXF (activation) and Sim2 (repression) action. Drebrin has been reported to be engaged in dendriticcytoskeleton modulation at synapses, and such a novel NXF signaling system on neural gene promoter may be a molecular target of the adverse effects of Sim2 in the mental retardation of Down's syndrome.
Pyrethroid isomers (four isomers of permethrin and fenvalerate, eight isomers of cypermethrin, and deltamethrin and its seven isomers) and a racemic mixture of fenpropathrin were examined for degradation rate and route in two Japanese upland soils under the same experimental conditions. Degradation of each pyrethroid isomer was studied at 25C under dark conditions with the 14C-labeled chemicals. The traps isomers of permethrin, cypermethrin and deltamethrin degraded more rapidly than the corresponding cis isomers, and the aS epimers of cypermethrin, fenvalerate and deltamethrin degraded faster than the corresponding chR epimers. The degradation rate of cypermethrin or deltamethrin isomers decreased in order of (trans. aS) > (trans. aR) > (cis, aS) > (cis, c R). The cis Jtrans or aR/aS isomerization hardly occurred in the soils. Based on the minimum and maximum half-lives of individual isomers of each pyrethroid, permethrin was judged to have decomposed most rapidly, followed in decreasing order by cypermethrin, deltamethrin and fenvalerate, with only a slight difference between cypermethrin and deltamethrin. Larger amounts of 14C02 and ester cleavage products were formed in the soils treated with less persistent traps or aS isomers, whereas oxidation products retaining the ester linkage such as diphenyl-ether bondcleavage products and ring-hydroxylated products were of more importance in the soils treated with more stable cis or ceR isomers. A larger amount of bound 14C was formed with cis or caR isomers. Degradation of four isomers of a dichlorovinyl analogue of chrysanthemic acid, the acidic half of permethrin and cypermethrin molecules, was also examined in two soils.
The photodegradation of fenpropathrin [(RS)‐α‐cyano‐3‐phenoxybenzyl 2,2,3,3‐tetramethylcyclopropanecarboxylate] (I), in water, on soil and on plant foliage, was investigated using 14C‐preparations labelled separately at the cyano group, cyclopropyl‐C1 or in the benzyl ring. On exposure to sunlight, I was photodecomposed with initial half‐lives of >6 weeks in distilled water, 6.0 weeks in humic acid aqueous solution, 2.7 weeks in river water, 1.6 weeks in sea water and 0.5 of a day in 2% aqueous acetone. A triplet photosensitiser, acetone, together with naturally occurring substances in river and sea water, including humic acid, enhanced the photodegradation of I. On three kinds of soil, I was rapidly photodegraded with initial half‐lives of 1–5 days, whereas it was fairly photostable on a mandarin orange leaf. The photoreactions involved were: decarboxylation, hydration of the cyano group to carboxamide, cleavage of the ester or the diphenyl ether linkage, hydrolysis of the carboxamide group to carboxyl, and hydroxylation at either or both of the gem dimethyl groups. The predominant reactions in water were decarboxylation, ester bond cleavage and photo‐induced evolution of [14C] carbon dioxide from the [14C] cyano label; on soil, hydration or ester bond cleavage predominated. The hydration was also of importance in river and sea water. Decarboxylation did not occur on soil and plant foliage.
Chymostatin, a chymotrypsin inhibitor, was shownto be a mixture of components A, B and C. The structure of component A as determined to be iV-[((S)-l-carboxy-2-phenylethyl)-Components B and C differed only in that the L-leucyl residue was replaced by l-valine and lisoleucine, respectively.A microbial product, chymostatin, which inhibits chymotrypsin and papain, was discovered by H. Umezawaet al.v in 1970 by testing the anti-chymotrypsin activity of culture filtrates. Wewish to report the structural elucidation of chymostatin.Since the amino acid analysis of different samples gave variable ratios of phenylalanine, leucine, valine and isoleucine, chymostatin was considered to be a mixture of similar peptides with minor differences. Attempts to separate the componentswere unsuccessful. Chymostatin was sparingly soluble in all solvents except acetic acid and dimethylformamide. It gave a positive test with triphenyltetrazolium chloride but was negative to ninhydrin, suggesting the presence of a reducing function and the absence of a free amino group. Partial hydrolysis of chymostatin with 1 n hydrochloric acid in acetic acid (sealed tube, 120°C, 40 minutes) gave leucine, valine and a trace of isoleucine, together with three ninhydrin-negative compounds: 1 [monohydrochloride-monohydrate: mp 216~220°C (dec.)], 2 (a mixture of 2a, 2b and 2c) and 3 (mp 47°C) (Chart 1).Hydrolysis of 1 with 1 n hydrochloric acid at 145°C for 72 hours gave DL-phenylalanine, a new basic amino acid (4) and ninhydrin-negative compounds (7a and 7b) which will be described later in detail.The compound 4 (4a and 4b) showed three pKa values (<2, 7.5 and > 12) in water, suggesting the presence of a carboxyl, an amino and a strong basic group. On treatment with anhydrous methanol and acetic anhydride, 4 was converted into its di-N-acetyl-monomethyl ester (5). The nature of the derivative was confirmed by the NMRspectrum. The high resolution mass spectrum of 5 showed m\e 228.1215, which corresponds to M+-CH2=C=O. From these results, and their elemental analyses the most probable empirical formulae of 5 and 4 were concluded to be C11H18N4O4and C6Hi2N4O2, respectively.However, the NMRspectrum (in D2Oand 1 equivalent DC1) of 4 showed that it was a mixture of diastereomers containing a common sequence of -CH2-CH2-CH-CH-. This was supported by i i the presence of a-methine doublets at 8 4.65 and 4.67 in the NMRspectrum of 5 which was also mixture
On exposure to sunlight, fenitrothion was photodecomposed with the half-lives of 0. 6-1. 0 days in distilled water, 1. 5, 1. 0, and 0. 9 days in buffer solutions at pH 3, 7 and 9 respectively, and 0. 9-1. 1 days in natural river and sea water. The quantum yield was determined to be 8. 0 X 10-4 (at 313 nm in distilled water), and the half-life of disappearance at 40 degree north latitude was calculated to be 1. 4 days in fall. Fenitrothion applied on two kinds of soil thin layer plates promptly disappeared through photodegradation and volatilization, with the half-life of approximately 1 day. The insecticide underwent photo-induced oxidation of P=S to P=O, oxidation of the aryl methyl group to the carboxyl group, reduction of the nitro group to the amino group, coupling of the carboxy group with the amino group leading to the formation of the dimeric compound, cleavage of the P-O-aryl or P-O-methyl linkage, isomerization, formation of the benzoisoxazole derivative with subsequent formation of the seven-membered ring (azepine derivative) through Beckmann rearrangement, and photomineralization of the aromatic ring to carbon dioxide in water, and oxidation of P=S to P=0 and cleavage of the P-O-aryl linkage on soil. The formation of the major photoproducts in water was pH dependent. The carboxy derivative oxidized at the aryl methyl group of fenitrothion was predominant in distilled water at pH 5. 9 and in buffer solutions at pH 3 and 7, while the dimeric compound, composing of the carboxy derivative of fenitrothion and the corresponding amino analog, was more predominantly formed in buffer solutions at pH 7 and 9, and natural river (pH 7. 4) and sea (pH 7. 8) water. On prolonged exposure to sunlight, these photoproducts were degraded further to 14C02 and the unextracted residues, which were considered to be the polymerized compounds like humic acid and other highly polar products. Fenitrothion underwent hydrolysis through neutral (pH independent) and basecatalyzed processes below pH 7 and above pH 10 respectively, while both reactions occurred between pH 7 and pH 10. The half-lives of disappearance by hydrolysis within the ranges of pH 5-9, normally found in natural water, were about 200-630 days at 15°C, 17-61 days at 30°C, and 4-8 days at 45°C. The product cleaved at the P-O-aryl linkage was predominant above pH 10, while the product cleaved at the P-O-methyl linkage was predominant below pH 8. The rates and pathways of degradation of fenitrothion by photolysis and hydrolysis in natural river and sea water were similar to those in buffer solutions at the same pH.
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