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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The susceptibility of proteins in the myelin membrane to proteases was studied. Lyophilized rat brain myelin suspended in water was subjected to controlled proteolytic digestion with pure trypsin (N-tosyl-l-phenylalanine chlo-romethyl ketone treated, 5 units/mg of myelin), and proteins remaining in the pellet were analyzed by sodium dode-cyl sulfate-polyacrylamide gel electrophoresis. Under these conditions, large basic protein (LBP) was completely hydro-lyzed in 5–10 min, proteolipid proteins remained largely intact until 60 min, whereas Wolfgram protein (WP) was progressively degraded from 10 min onward with the simultaneous appearance of a new protein band with a molecular weight of 35K. A similar pattern was obtained on treatment with chymotrypsin or subtilisin. The 35K protein band was shown to be derived from WP by its immunological cross-reactivity with WP antibodies. Western blot analysis showed that 35K protein is the only major breakdown product of WP under these conditions. Treatment with higher concentrations of trypsin (〉20 units/mg of myelin) resulted in the degradation of all the myelin proteins. Essentially all the 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNP) activity was observed in the myelin pellet after controlled or drastic digestion with trypsin. It is concluded that the major fragment of WP (35K) is located in the hydrophobic milieu of the bilayer, relatively inaccessible to trypsin, whereas a portion (20K) of the WP is exposed to the cytoplasmic side (major dense line), like LBP, and that peptide fragments (〈 14K) that remained in the myelin membrane lipid bilayer after trypsin digestion could exhibit CNP activity.
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  • 2
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Copper toxicity has been studied in three nickel-resistant strains ofNeurospora crassa (NiR1, NiR2, and NiR3). NiR1 and NiR2, but not NiR3, were two-to threefold more sensitive than the parent wild strain (N. crassa EM 5297a) to Cu2+ on a normal N medium. On a nitrate N medium, Cu2+ was 16-fold more toxic to NiR3 because of reduced synthesis of nitrite reductase; NiR1 and NiR2 were only fivefold more sensitive to Cu2+, and nitrite reductase synthesis was unaffected. Mn2+ reversed Cu2+ toxicity on normal N medium only, in all strains. Fe3+ counteracted Cu2+ toxicity on nitrate N medium also. It was shown that Cu2+ affected Fe3+ utilization for nitrite reductase synthesis in NiR3 only and that in these Ni2+-resistant strains, Fe3+ antagonized effects of Cu2+, but not of other toxic metal ions.
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  • 3
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Uptake of Co2+ by three nickel-resistant strains (NiR1, NiR2, and NiR3) ofNeurospora crassa that differed in resistance to Co2+ has been studied. Uptake was linear with Co2+ concentration (up to 1 mM), with time (up to 6 h), and with pH between 3 and 6. Uptake rates were in the order NiR2〉NiR1〉NiR3. In all strains, there was gradual increase in Co2+ uptake between 10° and 28°C, with a much sharper increase between 28° and 40°C. Metabolic inhibitors decreased Co2+ uptake partially in all strains, except for KF in NiR3. About 50–80 μg Co2+/100 mg dry weight was surface bound. Ni2+, Zn2+, and Mn2+ competed with Co2+, the effects being strain specific. Mg2+ inhibited Co2+ uptake in all strains with preformed mycelia. In NiR1 and NiR2 only with young mycelia (40 h old) was Mg2+ inhibitory to Co2+ uptake,during growth in the presence of Co2+. The results suggested the presence of two transport systems for Co2+ in NiR1 and NiR2, only one of which was sensitive to Mg2+; in contrast, NiR3 had a single system, which was sensitive to Mg2+.
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  • 4
    ISSN: 1573-0972
    Keywords: Biosorbent ; biosorption ; metal ions ; Phormidium valderianum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Alkali-extracted biomass of Phormidium valderianum BDU 30501, a marine filamentous, non-heterocystous cyanobacterium adsorbed more than 90% of cadmium ions from solutions containing 0.1–40 mM. Cadmium binding accounted up to 18% of biomass weight (w/w). The algal biosorbent was also efficient is sequestering metal ions (Cd2+, Co2+, Cu2+, Ni2+) from a mixture. Biosorbent placed in dialysis tubing could concentrate Cd2+ (50–65%) from 1l solution (10 and 100 ppm) at equilibrium. Biosorbent immobilized in polyvinyl foam also removed cadmium and cobalt efficiently, but required longer contact times (24 h). Most of the bound metal ions (〉 80%) could be desorbed with 0.1 M HCl or EDTA, while other reagents were less efficient in the order: H2SO4 〉 NH4Cl 〉 CaCl2 〉 Na2SO 4 〉 KSCN 〉 KCl 〉 NH4OH 〉 NaHCO3. The regenerated biosorbent retained 80% of the initial binding capacity for Cd2+ and 50% binding capacity for Co2+ up to three cycles of reuse. Infrared spectra of the biosorbent preparation suggested carboxyl groups to be the primary sites for metal binding.
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  • 5
    ISSN: 1572-8773
    Keywords: biosorption ; decontamination ; cadmium ; calcium ; magnesium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Alkali extracted mycelial biomass from Aspergillus niger, referred to as Biosorb, was found to sequester metal ions (Cd2+, Cu2+, Zn2+, Ni2+ and Co2+) efficiently both from dilute and concentrated solutions upto 10% of its weight (w/w). Sequestration of metal ions from a mixture was also efficient but with attendant antagonisms. The kinetics of metal binding by Biosorb indicated that it is a rapid process and about 70–80% of the metal is removed from solution in 5 min followed by a slower rate. The mechanism of metal binding is shown to be due to exchange of calcium and magnesium ions of the Biosorb during which equimolar concentrations of both the ions were released into the medium. Following this an efficient procedure for the regeneration and reuse of Biosorb was standardized by washing the biosorbent with calcium and magnesium solution (0.1 m). Biosorbents prepared from Neurospora, Fusarium and Penicillium also exhibited similar mechanisms for metal ion binding, though they had a lower metal binding capacity when compared with Biosorb. Chemical modification of carboxylic acid functional groups of the Biosorb resulted in loss of 90% of metal binding capacity which could not be restored even on regeneration. The significance of this finding on the metal sequestration mechanisms of microbial biosorbents is discussed.
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  • 6
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Mycelial biomass of wild type and a Co2+-resistant N.crassa (cor) was used to remove Co2+ from aqueous media. Mycelia obtained from growth in nitrate N-medium (NaNO3) was more effective than ammonium N-medium (NH4NO3), in removing Co2+. Co2+-resistant N.crassa cor was more efficient than wild type in removing Co2+ from medium containing higher concentrations (500 mg/L). Metal removal was linear up to 12 h at which 35–60% Co2+ is depleted from medium, reaching near saturation by 24 h (90% removal). Co2+ removal was as efficient even from pure solutions and sodium azide inhibited the process up to 60%. Cell walls prepared from nitrate N-medium grown mycelia bound 3–5 fold more Co2+ when compared to ammonium N-medium. The importance of bioaccumulation and biosorption in bioremediating toxic metal ions from effluents is discussed.
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