Patterns of oligosaccharide production by polygalacturonases

The products of hydrolytic action of 18 enzyme preparations at pH 3·5 and 5·5 on pectate were analyzed by gel-filtration chromatography early in the course of reaction (8–15% hydrolysis), and at a time 10 times that required for 10% hydrolysis. The degree of hydrolysis at the latter time varied from 25 to 74%. Three patterns of oligosaccharide production could be distinguished: endo-hydrolysis, exo-hydrolysis, and that due to S-polygalacturonase. The initial products of endo-hydrolysis were mixed oligosaccharides 5–30 units long; monomer and dimer appeared early but represented less than 2% of the products until late in the reaction. exo-Polygalacturonase (not entirely free of endo-) showed predominant production of the monomer and was clearly evident when mixed with four parts of endo-polygalacturonase. The time course of reducing group production by highly purified S-polygalacturonase could be reproduced by the above mixture of exo- and endo-polygalacturonases, but the pattern of products and the pH relations could not. The initial products of S-polygalacturonase were monomer, dimer and pentamer with lesser amounts of trimer and tetramer. After the hydolysis of the polymer and large oligomers, the pentamer was attacked by S-polygalacturonase, in the same way that the accumulated hexamer, etc. were finally hydrolysed by the endo-polygalacturonase.     

外源5-氨基乙酰丙酸对NaCl胁迫下黑果枸杞幼苗生理及生长的影响

5-氨基乙酰丙酸(ALA)是植物血红素、叶绿素等四吡咯化合物的关键生物合成前体,对植物适应非生物胁迫至关重要。为验证外源ALA对黑果枸杞幼苗生理生长的影响,该研究用300 mmol·L^-1 NaCl和不同浓度(0、5、10、15、20、25 mg·L^-1)的ALA共同处理黑果枸杞幼苗,并测定其相关的生理指标和生长指标,综合评价各处理幼苗的耐盐性。结果表明：(1)NaCl胁迫使黑果枸杞幼苗总生物量和叶片总叶绿素、类胡萝卜素、可溶性糖含量以及过氧化物酶(POD)活性较CK分别显著降低了33.39%、19.06%、24.38%、39.57%和47.91%(P<0.05),使黑果枸杞幼苗脯氨酸和丙二醛的含量较CK分别显著增加了165.74%和49.16%。(2)当外源ALA和NaCl同时处理时,黑果枸杞幼苗叶片类胡萝卜素和丙二醛含量、POD和过氧化氢酶(CAT)活性以及株高、总生物量均恢复至对照水平,叶片总叶绿素和脯氨酸含量以及SOD活性较CK显著增加。(3)黑果枸杞幼苗叶片叶绿素和脯氨酸含量以及抗氧化酶活性、生物量等指标随ALA浓度增加均呈先...     

Fullerol-fluorescein isothiocyanate phosphorescent labeling reagent for the determination of glucose and alkaline phosphatase

The active -OH group in fullerol (F-ol) could react with the dissociated -COOH group in fluorescein isothiocyanate (FITC) to form F-ol-(FITC)_n, which could emit room temperature phosphorescence (RTP) signal of F-ol and FITC on acetate cellulose membrane (ACM), respectively. Their RTP signals were enhanced by N,N-dimethylaniline (DMA). The labeling reaction between the -NCS group of FITC in DMA-F-ol-(FITC)_n and the -NH₂ group in wheat germ agglutinin (WGA) produced DMA-F-ol-(FITC)_n-WGA, which could further take affinity adsorption (AA) reaction with bioactive substances (BS), such as glucose and alkaline phosphatase (AP), to produce DMA-F-ol-(FITC)_n-WGA-BS. Both of these two products could maintain the good RTP characteristics of F-ol and FITC. Based on the facts above, a new phosphorescent labeling reagent, DMA-F-ol-FITC, was developed, and a new affinity adsorption solid substrate room temperature phosphorimetry (AASSRTP) for the determination of BS was established. This method was applied to the determination of BS in human serum and the diagnosis of diseases, with the results agreeing very well with those of enzyme-linked immunosorbent assay (ELISA). The mechanism of DMA-F-ol-(FITC)_n labeling of WGA and AASSRTP for the determination of BS is discussed.     

Laboratory Hints from the Literature

Chaze, J. Sur le mode de formation et la detection des alcaloides dans la plantule de tabac. Bull. d'Histol. Appl., 5, 253. 1928.

Nan, Yao. Sur un fixateur cytologique particulièrement adapté aux tissues des insectes. Bull. d'Histol. Appl., 4, 71, 1927.

Reichardt, H., and Wetzel, A. Paraffineinbettungsmethode nach vorhergegangener Zelloidindurchtränkung unter Vermeidung der härtenden Intermedien, Xylol, Benzol, Chloroform. Zeit. f. wiss. Mikr., 45, 476-479. 1928.

Erb, N. M. A rapid stain for direct miroscopic examination of milk. J. Lab. & Clin. Med., 14, 377. 1929.

Galesesco, P., and Bratiano, S. Coloration des graisses par l'extrait alcoolique de Daucus carota. Compt. Rend. Soc. Biol., 99, 1460. 1928.

Goldner, J' Résultats obtenus chez la seiche par l'emploi de divers colorants vitaux Comp. Rend. Soc. Biol., 99, 1323. 1928.

Hadjioloff, A. Une modification rapide de la méthode de Weigert-Pal. Bull. d'Histol. Appl., 5, 431-434. 1928.

Hausdorf, G. Farbung zur Darstellung reifer Samenzellen im Hodenschnittpraparat. Zeit. f. wiss. Mikr., 44, 327-328. 1927.

Houcke, E. Emploi des colorants mixtes en technique histologique. Comp. Rend. Soc. Biol., 99, 783. 1928.

Houcke, E. Emploi des mélanges de fuchsines et de blues basiques pour la coloration histologique. Comp. Rend. Soc. Biol., 99, 786. 1928.

Houcke, E. Emploi du mélange rhodamine-blue de méthylène dans la coloration des tissus splénique et lymphcïde. Comp. Rend. Soc. Biol., 99, 788. 1928.

Lillie, R. D. Erne Schnellmethode zur Toluidinblau-Schleimfarbung. Zeit. f. wiss. Mikr., 45, 381. 1928.

Ochs, Georg Wilhelm. Über den Einfluss der Temperatur auf die Färbung von Blutausstrich-Präparaten. Folia Hematologica, 37, 241-257. 1928.

Verne, Jean. Une nouvelle coloration élective de la myeline. Bull. d'Histol. Appl., 5, 223-224. 1928.     

Potential role of bacterial extracellular polymeric substances as biosorbent material for arsenic bioremediation

Carcinogenic effects of arsenic through consumption of contaminated water are an alarming threat and there is an emergent need to reduce extremely high levels of toxic arsenic from environment. Bacterial biofilms produce polyanionic extracellular polymeric substance (EPS) that is considered an excellent biosorbent material for the remediation of toxic metals and metalloids. This study was aimed to investigate the role of bacterial EPS in arsenic bioremediation. EPS was extracted from biofilm forming and arsenic reducer bacterial strains that were isolated from industrial waste water and characterized biochemically. Fourier transform infrared spectroscopy was also performed to study functional groups. Both Exiguobacterium profundum PT2 and Ochrobactrum ciceri SW1 exhibited enhanced EPS production in the presence of arsenic. Arsenic stress increased protein and carbohydrate contents in the EPS of both bacterial strains as indicated by the peaks of 1363 to 1613 and 1035 to 1218?cm^?1 wavenumbers, respectively to cope with arsenic present in the surroundings. Shifting of peaks in As⁵⁺ treated samples from 1363 to 1379, 847 to 800 and 1211 to 1134?cm^?1 demonstrated the involvement of proteins, carbohydrates and phosphates in the sequestration of arsenic. Scanning electron microscopic examination of EPS revealed structural alterations such as the presence of closely embedded large clumps with interstitial spaces between stacked layers of the EPS of E. profundum PT2 treated with As⁵⁺ displayed the enhanced polysaccharide content and arsenic sorption. Therefore, increased production of bacterial EPS with large number of polyanionic functional groups on its surface having tendency to sequester arsenic through electrostatic or covalent interactions presented EPS an excellent biosorbent material for arsenic bioremediation.     

The effect of humic substances on the toxicity of aluminium to adult rainbow trout, Oncorhynchus mykiss (Walbaum)

Some physiological parameters were measured in adult rainbow trout during a 10-day exposure to 180 μg Al_total l⁻¹ in acid water (pH 4.7) with or without humic substances (10 mg l⁻). The fish were acclimatized to pH 5.0 for 7 days prior to the experimental treatments.
Chemical analyses revealed that, in the presence of human substances, 74–80% of the A1 was organic bound, while in the absence of humic substances most of the Al(987percnt;) occurred in the inorganic form.
Al bound to humic substances (13–150 μg l⁻¹) did not alter the plasma NaCl-concentration, nor the haematocrit value, of rainbow trout during an exposure period of 10 days. This contrasts with the high death rate obtained within 2–3 days when most of the A1 (175 μg l⁻¹) was in the inorganic form. The lethality was accompanied by a 25% decrease in the plasmaconcentration of NaCl and a doubling of the haematocrit value. Bulk analysis revealed that when the metal was present in inorganic forms the total Al content of the gills (75 μg A1 g⁻¹ wet weight) was 15 times higher than when it was present as bound to the humic substances. These experiments showed that the accumulation of A1 at the gills was accompanied by physiological disturbances, both being a function of the chemical speciation of Al.     

Influence of EPS isolated from thermophilic sulphate-reducing bacteria on carbon steel corrosion

Extracellular polymeric substances (EPS) were isolated by centrifugation of thermophilic sulphate-reducing bacteria (SRB) grown in API-RP38 culture medium. The protein and polysaccharide fractions were quantified and the highest concentrations were extracted from a 14-day old culture. The effect of EPS on carbon steel corrosion was investigated by electrochemical techniques. At 30°C, a small amount of EPS in 3% NaCl solution inhibited corrosion, whilst excessive amounts of EPS facilitated corrosion. In addition, the inhibition efficiency of EPS decreased with temperature due to thermal desorption of the EPS. The results suggest that adsorbed EPS layers could be beneficial to anti-corrosion by hindering the reduction of oxygen. However, the accumulation of an EPS film could stimulate the anodic dissolution of the underlying steel by chelation of Fe²⁺ ions.     

Isolation and characterization of cell-wall pectic substances from potato tuber

Exhaustive treatment of potato tuber tissues by purified endo-polygalacturonase from Aspergillus japonicus solubilized 95% of the total uronides of     

In vitro bioassay of sheep gastrointestinal mucus for nematode paralysing activity mediated by substances with some properties characteristic of SRS-A

A bioassay is described for determining the inhibition of nematode larval migration from agar by substances exerting a paralysing action.In the assay, larval migration was completely inhibited by the anthelmintic levamisole (25 μg/ml) whereas biogenic amines, and prostaglandins E₁ and E₂ at 50 μg/ml, were without effect. Mucus from the gastrointestinal tract of sheep resistant to nematode infection inhibited larval migration by up to 93% whereas mucus from heavily infected sheep or sheep reared helminth free did not significantly inhibit larval migration. Mucus from sheep resistant to Trichostrongylus colubriformis inhibited the migration of larvae of other nematode species.The larval migration inhibitory (LMI) activity of mucus from resistant sheep was associated with components having some properties of slow reacting substance of anaphylaxis (SRS-A).Faecal samples from resistant sheep possessed significantly more LMI activity than faecal samples from heavily infected sheep or sheep reared helminth free. The level of LMI activity in the faeces of sheep undergoing challenge infection may be a useful indicator of the sheep's resistance status.The presence of the larval migration inhibitory activity in sheep mucus is discussed in relation to resistance to infection.