An Evidence for the Repair of Double-Strand Scissions in DNA of Micrococcus radiodurans after Alpha Bombardment

The conversion of prochaetoglobosins as plausible precursors into mycotoxin chaetoglobosin A (1) in a cell-free system of Chaetomium subaffine was unsuccessful. However, reductase activity of the 20-keto-analogues (1), and prochaetoglobosins II (5) and III (6) were found in a microsomal fraction of this fungi. Two new metabolites of chaetoglobosins, named chaetoglobosin F_ex (2) and 20-dihydro-chaetoglobosin A (3), were also isolated from the same micro-organisms. Their structures were elucidated by spectroscopic data and chemical transformation.     

Purification and properties of a heat-stable inulin fructotransferase from Arthrobacter ureafaciens

An inulin fructotransferase producing difructose dianhydride I (EC 2.4.1.200) was purified from Arthrobacter ureafaciens A51-1. It had maximum activity at pH 5.5 and 45 °C, and was stable up to 80 °C. This is the highest thermal stability for this enzyme reported to date. The molecular mass was estimated to be 38000 by SDS-PAGE, and 61000 by gel filtration. It was therefore estimated to be a dimer.     

A chemically modified lipase preparation for catalyzing the transesterification reaction in even highly polar organic solvents

Acylation of Pseudomonas cepacia lipase with Pyromellitic dianhydride to modify 72% of total amino groups was carried out. Different organic solvents were screened for precipitation of modified lipase. It was found that 1,2-dimethoxyethane was the best precipitant which precipitated 97% protein and complete activity. PCMC (protein coated microcrystals), CLPCMC (crosslinked protein coated microcrystals), EPROS (enzyme precipitated and rinsed with organic solvents) and pH tuned preparations of modified and unmodified lipase were prepared and used for carrying out transesterification reaction with n-octane and dimethyl formamide (DMF) as reaction medium. In n-octane, among all the preparations, CLPCMC of modified lipase gave highest rate (1970 nmol min⁻¹ mg⁻¹) as compared to unmodified pH tuned lipase (128 nmol min⁻¹ mg⁻¹). In DMF, with both 1% (v/v) and 5% (v/v) water content, CLPCMC showed highest initial rate of 0.72 and 7.2 nmol min⁻¹ mg⁻¹, respectively. Unmodified pH tuned lipase showed no activity at all in DMF with both 1% and 5% (v/v) water content.     

Purification and characterization of a heat stable inulin fructotransferase (DFA I-producing) from Arthrobacter pascens a62-1

An inulin fructotransferase (DFA I-producing) [EC 2.4.1.200] from Arthrobacter pascens a62-1 was purified and the properties of the enzyme were investigated. The enzyme was purified from culture supernatant of the microorganism 58.5 fold with a yield of 8.32% using Super Q Toyopearl chromatography and butyl Toyopearl chromatography. It showed maximum activity at pH 5.5 and 45 °C and was stable up to 75 °C. This heat stability was highest in the inulin fructotransferases (DFA I-producing) reported until now. The molecular mass of the enzyme was estimated to be 37,000 by SDS-PAGE and 60,000 by gel filtration, and was considered to be a dimer. The N-terminal amino acid sequence (20 amino acid residues) was determined as Ala-Asn-Thr-Val-Tyr-Asp-Val-Thr-Thr-Trp-Ser-Gly-Ala-Thr-Ile-Ser-Pro-Tyr-Val-Asp.     

Adsorption of ethylenediaminetetraacetic dianhydride modified oxalate decarboxylase on calcium oxalate

We used ethylenediaminetetraacetic acid dianhydride (EDTAD) to modify oxalate decarboxylase (OXDC) to improve its adsorption on calcium oxalate stones. The modified sites were identified by Ultra performance liquid chromatography-mass spectrometry (UPLC-MS) and the adsorption mechanism of the EDTAD-modified OXDC on calcium oxalate (CaOx) was investigated. We investigated adsorption time, initial enzyme concentration, temperature and solution pH on the adsorption process. Data were analyzed using kinetics, thermodynamics and isotherm adsorption models. UPLC-MS showed that EDTAD was attached to OXDC covalently and suggested that the chemical modification occurred at both the free amino of the side chain and the α-NH₂ of the peptide. The adsorption capacity of the EDTAD-OXDC on calcium oxalate was 53.37% greater than that of OXDC at the initial enzyme concentration of 5 mg/ml, pH = 7.0, at 37° C. The modified enzyme (EDTAD-OXDC) demonstrated improved oxalate degradation activity at pH 4.5?6.0. Kinetic data fitting analysis suggested a pseudo second order kinetic model. Estimates of the thermodynamic parameters including ΔG⁰, ΔH⁰ and ΔS⁰ of the adsorption process showed it to be feasible, spontaneous and endothermic. Isotherm data fitting analysis indicated that the adsorption process is reduced to monolayer adsorption at a low enzyme concentration and to multilayer adsorption at a high enzyme concentration. It may be possible to apply OXDC to degradation of calcium oxalate stones.     

Biodegradable superabsorbent hydrogels derived from cellulose by esterification crosslinking with 1,2,3,4-butanetetracarboxylic dianhydride

Superabsorbent hydrogels were prepared from native celluloses dissolved in lithium chloride and N-methyl-2-pyrrolidinone (LiCl/NMP) by esterification crosslinking with 1,2,3,4-butanetetracarboxylic dianhydride (BTCA). Subsequent conversion of the unreacted carboxyl groups to sodium carboxylates by the addition of aqueous NaOH was performed to enhance the water affinity of the gels. The absorbency of the products was strongly dependent on the amount of BTCA that was esterified to cellulose, and the highest absorbency was observed for the hydrogel composed of approximately 0.25 molecules of BTCA per anhydroglucose unit (AGU) of cellulose. Furthermore, it was confirmed that the absorbency was enhanced as the average degree of polymerization (DP) of the starting cellulose increased. The use of cotton cellulose with a high DP of about 2400 produced a hydrogel with an absorbency of 720 times its dry weight, which exceeded the absorbency of commercial crosslinked sodium polyacrylate superabsorbent hydrogel (SPA). The hydrogels exhibited good biodegradability, with a maximum degradation of 95% within 7 days using cellulase.     

Enhancement of spermidine content and antioxidant capacity in transgenic pear shoots overexpressing apple spermidine synthase in response to salinity and hyperosmosis

In our previous work, an apple spermidine synthase (SPDS)-overexpressing transgenic European pear (Pyrus communis L. 'Ballad'), line no. 32 (#32), demonstrated attenuated susceptibility to stress treatment. In the current paper, changes in enzymatic and non-enzymatic antioxidant capacity of the transgenic pear (line #32) were investigated in response to NaCl or mannitol stress. Under non-stressed conditions (before stress treatment), spermidine (Spd) contents and SPDS activity of line #32 were higher than those of the non-transformant (wild type). However, no significant differences were detected between line #32 and the wild type as regards contents of malondialdehyde (MDA) and H2O2, and activities of antioxidant enzymes like superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR). When exposed to NaCl or mannitol stress, both the wild type and line #32 exhibited accumulation of Spd with the latter accumulating more. The transgenic line contained higher antioxidant enzyme activities, less MDA and H2O2 than the wild, implying it suffered from less injury. These results suggested that increase of Spd content in the transgenic line could, at least in part, lead to enhancing enzymatic and non-enzymatic antioxidant capacity.     

Evaluation of biological properties of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride derivatives and their ability to inhibit hexokinase activity

This investigation has explored the properties of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BDTA) derivatives with regard to their being prospective inhibitors of hexokinase II (HKII). A pluripotent embryonic carcinoma cell line P19 (ECC), was used as the biological target for newly generated potential inhibitors of HKII. The results obtained from Virtual High-Throughput Screening (VHTS), molecular modeling and biological activity studies showed BDTA to be a promising leading structure with a good binding score and simplest functionalization. The inhibitory effect was measured after 72 h incubation. Of selected BDTA derivatives, the most active was compound 3b, containing 3-hydroxyphenyl moiety in the para position, being able at 100 μM to decrease the mass of differentiated P19dCs cells by 30%, changing both the mitochondrial transmembrane potential and reactive oxygen species level. Under these conditions, only compound 3b had the ability to decrease hexokinase activity in a dose-dependent manner.     

Removal of Ca(II) and Mg(II) from aqueous single metal solutions by mercerized cellulose and mercerized sugarcane bagasse grafted with EDTA dianhydride (EDTAD)

In a previous work, chemically modified cellulose (EMC) and sugarcane bagasse (EMMB) were prepared from mercerized cellulose (MC) and twice-mercerized sugarcane bagasse (MMB) using ethylenediaminetetraacetic dianhydride (EDTAD) as modifying agent. In this work we described in detail the modification of these materials in function of reaction time and EDTAD amount in the reaction media. The resistance of ester bond at pH 1, 2, 11, and 12 was also evaluated by FTIR. The results were used to model the hydrolysis process and a kinetic model was proposed. The modified materials (EMMB and EMC) were used to adsorb Ca²⁺ and Mg²⁺ ions from aqueous single solutions. The adsorption isotherms were developed at two pH values. These materials showed maximum adsorption capacities for Ca²⁺ and Mg²⁺ ions ranging from 15.6 to 54.1 mg/g and 13.5 to 42.6 mg/g, respectively. The modified material from sugarcane bagasse (EMMB) showed larger maximum adsorption capacities than modified material from cellulose (EMC) for both metals.     

Chemical modification of alpha-chymotrypsin for obtaining high transesterification activity in low water organic media

Alpha-chymotrypsin was made more hydrophilic by modifying 11 (out of 16) ε-amino groups with pyromellitic dianhydride. The hydrophilic preparation was precipitated with n-propanol. This preparation gave significantly higher initial rates at the optimum a_w (127.51 nmol mg^?1 min^?1 in n-octane and 21.30 nmol mg^?1 min^?1 in acetonitrile at a_w=0.33) compared with the lyophilized preparation (53.50 nmol mg^?1 min^?1 in n-octane and 0.26 nmol mg^?1 min^?1 in acetonitrile at a_w=0.97). FT-IR showed that the precipitate of modified alpha-chymotrypsin has a higher content of alpha-helices and beta-sheets compared to the lyophilized powder.