The Experts below are selected from a list of 159 Experts worldwide ranked by ideXlab platform
Uttam Chand Banerjee - One of the best experts on this subject based on the ideXlab platform.
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TranSformation of Rifamycin B with growing and reSting cellS of Curvularia lunata.
Enzyme and Microbial Technology, 1993Co-Authors: Uttam Chand BanerjeeAbstract:Growing and reSting cell SyStemS of Curvularia lunata were uSed for the tranSformation of Rifamycin B to Rifamycin S. In the caSe of growing cellS, Rifamycin B waS added at the time of inoculation and at the different phaSeS of growth. IntereStingly, it waS found that C. lunata could grow in the preSence of Rifamycin B and could convert Rifamycin B to Rifamycin S. Growing cellS 24 and 48 h of age were capable of tranSforming Rifamycin B. ReSting cellS, cultivated at the exponential or early Stationary phaSe, were found to be very active, and the reSting cellS of different ageS were repeatedly uSed for the tranSformation reaction. Growing cellS of 72 and 96 h were not capable of tranSforming Rifamycin B, whereaS reSting cellS of Similar ageS were very active. Due to the adSorption of RifamycinS by the growing and reSting cellS of C. lunata, the Stoichiometric yield of Rifamycin S waS not obtained.
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StudieS on Rifamycin OxidaSe Immobilized on K-Carrageenan Gel
Biomaterials Artificial Cells and Immobilization Biotechnology, 1993Co-Authors: Uttam Chand BanerjeeAbstract:Rifamycin oxidaSe from Curvularia lunata var. aeria waS immobilized on kappa-carrageenan gel where the enzyme Showed excellent catalyzing activity and operational Stability. FactorS affecting the activity of immobilized enzyme preparation Such aS pH and temperature were inveStigated. ThermoStability of the immobilized enzyme preparation waS checked at 30 and 40 degreeS C and it waS found that the thermoStability of the immobilized Rifamycin oxidaSe activity haS increaSed compared to free enzyme. TranSformation of Rifamycin B to Rifamycin S waS alSo carried out with the immobilized enzyme preparation. Kappa-carrageenan immobilized Rifamycin oxidaSe waS alSo reuSed Several timeS for the tranSformation of Rifamycin B to Rifamycin S.
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TranSformation of Rifamycin B with Soluble Rifamycin oxidaSe from Curvularia lunata
Journal of Biotechnology, 1993Co-Authors: Uttam Chand BanerjeeAbstract:AbStract TranSformation of Rifamycin B to Rifamycin S uSing Soluble Rifamycin oxidaSe from Curvularia lunata waS carried out in Shake flaSk and in a reactor. Optimum tranSformation temperature waS found to be at 50°C but, from the practical point of view, all the tranSformation reactionS were carried out at 28°C. In non-Stirring condition it took 50 h to tranSform the 1% (w/v) Solution of Rifamycin B, while in Stirring condition (200 rpm) it took only 3 h. Five percent enzyme Solution (activity 11 IU ml −1 ) waS found to be optimum for the tranSformation reaction. An aeration rate of 1–1.5 vvm waS maintained during tranSformation reaction in a batch reactor. With higher SubStrate concentration (3%, w/v) it took more time (7 h) to complete the tranSformation than with 1% (w/v) Rifamycin B (3 h). A few dropS of antifoam (polypropylene glycol) waS effective in SuppreSSing the foam formed during aeration in the reactor and it did not interfere in the iSolation of Rifamycin S.
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Characterization of Rifamycin oxidaSe immobilized on alginate gel.
Biomaterials artificial cells and immobilization biotechnology : official journal of the International Society for Artificial Cells and Immobilization, 1993Co-Authors: Uttam Chand BanerjeeAbstract:Rifamycin oxidaSe of Curvularia lunata waS immobilized on alginate gel. The pH and temperature optima of the immobilized enzyme preparation were 6.5 and 50 degreeS C, reSpectively. TranSformation reaction waS carried out with the immobilized enzyme preparation. It took 8 h for the complete tranSformation of Rifamycin B (10 g/L) to Rifamycin S. The immobilized enzyme preparation waS found to be mechanically weak even in the preSence of CaCl2 in the reaction mixture. ReuSability StudieS Showed that the catalySt can not be repeatedly uSed very effectively.
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BiotranSformationS of RifamycinS: proceSS poSSibilitieS.
Biotechnology Advances, 1992Co-Authors: Uttam Chand Banerjee, B. Saxena, Yusuf ChistiAbstract:Rifampicin, an important antibiotic, iS manufactured by chemical converSion of Rifamycin S which iS obtained by the chemical modification of Rifamycin B. Rifamycin B iS a product of Nocardia mediterranei fermentationS. The chemical converSion of Rifamycin B to Rifamycin S haS many diSadvantageS: Strong acidic conditionS are required, heavy foam formation accompanieS tranSformation and the yieldS are low. ThiS review highlightS the developmentS in alternative, biochemical tranSformationS uSing enzymeS and cellS; the main focuS iS on tranSformationS carried out by Rifamycin oxidaSe.
Jef K. De Brabander - One of the best experts on this subject based on the ideXlab platform.
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Rifamycin BioSynthetic CongenerS: ISolation and Total SyntheSiS of RifSaliniketal and Total SyntheSiS of SaliniSporamycin and SaliniketalS A and B
Journal of the American Chemical Society, 2016Co-Authors: Yu Feng, Jun Liu, Yazmin P. Carrasco, John B. Macmillan, Jef K. De BrabanderAbstract:We deScribe the iSolation, Structure elucidation, and total SyntheSiS of the novel marine natural product rifSaliniketal and the total SyntheSiS of the Structurally related variantS SaliniSporamycin and SaliniketalS A and B. RifSaliniketal waS previouSly propoSed, but not obServed, aS a diverted metabolite from a bioSynthetic precurSor to Rifamycin S. Decarboxylation of Rifamycin provideS SaliniSporamycin, which upon truncation with loSS of the naphthoquinone ring leadS to SaliniketalS. Our Synthetic Strategy hinged upon a Pt(II)-catalyzed cycloiSomerization of an alkynediol to Set the dioxabicyclo[3.2.1]octane ring SyStem and a fragmentation of an intermediate dihydropyranone to forge a Stereochemically defined (E,Z)-dienamide unit. Multiple routeS were explored to aSSemble fragmentS with high Stereocontrol, an exerciSe that provided additional inSightS into acyclic Stereocontrol during Stereochemically complex fragment-aSSembly proceSSeS. The reSulting 11–14 Step SyntheSiS of SaliniketalS then enabled u...
Richard E. Chaisson - One of the best experts on this subject based on the ideXlab platform.
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Rifampin-ReSiStant TuberculoSiS in a Patient Receiving Rifabutin ProphylaxiS
The New England journal of medicine, 1996Co-Authors: William R. Bishai, Neil M.h. Graham, Susan M. Harrington, Christopher Page, Kristina Moore-rice, Nancy Hooper, Richard E. ChaissonAbstract:Drug-reSiStant tuberculoSiS haS become a major public health problem in the United StateS.1,2 In 1979 leSS than 1 percent of tuberculoSiS iSolateS from untreated patientS in New York City were reSiStant to rifampin, aS compared with 9 percent in 1991.3 Rifampin-reSiStant tuberculoSiS iS a SeriouS threat becauSe reSponSeS to therapy are more difficult to achieve and require longer courSeS of treatment.4–8 Rifabutin iS a derivative of Rifamycin S that iS recommended and widely uSed aS prophylaxiS againSt Mycobacterium avium complex infection in patientS infected with the human immunodeficiency viruS (HIV) who have low CD4 lymphocyte countS.9,10 Since . . .
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Antimicrobial activity of rifabutin. DiScuSSion
Clinical Infectious Diseases, 1996Co-Authors: C. M. Kunin, Fred M. Gordin, P. Philips, M. Tapper, Richard E. ChaissonAbstract:Rifabutin iS a Spiro-piperidyl-Rifamycin derived from Rifamycin-S. It iS Structurally related to rifampin and ShareS many of itS propertieS. Rifabutin haS a broad Spectrum of antimicrobial activity. It iS conSiderably more active than rifampin in vitro againSt the Mycobacterium avium complex (MAC), Mycobacterium tuberculoSiS, and Mycobacterium leprae. It alSo iS active againSt moSt atypical mycobacteria, including Mycobacterium kanSaSii, but Mycobacterium chelonae iS relatively reSiStant. Rifabutin alSo iS active againSt Staphylococci, group A Streptococci, NeiSSeria gonorrhoeae, NeiSSeria meningitidiS, HaemophiluS influenzae, HaemophiluS ducreyi, Campylobacter jejuni, Helicobacterpylori, Chlamydia trachomatiS, and ToxoplaSma gondii. It haS poor activity againSt Enterobacteriaceae and PSeudomonaS SpecieS. ThiS review focuSeS on the antimicrobial profile of rifabutin in relation to itS pharmacological propertieS. Special emphaSiS iS placed on itS in vitro activity againSt MAC and other mycobacteria, itS efficacy in cell culture and animal modelS, and itS potential aS a component of multidrug therapy for mycobacterial and other infectiouS diSeaSeS.
Yu Feng - One of the best experts on this subject based on the ideXlab platform.
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Rifamycin BioSynthetic CongenerS: ISolation and Total SyntheSiS of RifSaliniketal and Total SyntheSiS of SaliniSporamycin and SaliniketalS A and B
Journal of the American Chemical Society, 2016Co-Authors: Yu Feng, Jun Liu, Yazmin P. Carrasco, John B. Macmillan, Jef K. De BrabanderAbstract:We deScribe the iSolation, Structure elucidation, and total SyntheSiS of the novel marine natural product rifSaliniketal and the total SyntheSiS of the Structurally related variantS SaliniSporamycin and SaliniketalS A and B. RifSaliniketal waS previouSly propoSed, but not obServed, aS a diverted metabolite from a bioSynthetic precurSor to Rifamycin S. Decarboxylation of Rifamycin provideS SaliniSporamycin, which upon truncation with loSS of the naphthoquinone ring leadS to SaliniketalS. Our Synthetic Strategy hinged upon a Pt(II)-catalyzed cycloiSomerization of an alkynediol to Set the dioxabicyclo[3.2.1]octane ring SyStem and a fragmentation of an intermediate dihydropyranone to forge a Stereochemically defined (E,Z)-dienamide unit. Multiple routeS were explored to aSSemble fragmentS with high Stereocontrol, an exerciSe that provided additional inSightS into acyclic Stereocontrol during Stereochemically complex fragment-aSSembly proceSSeS. The reSulting 11–14 Step SyntheSiS of SaliniketalS then enabled u...
A. V. Rama Rao - One of the best experts on this subject based on the ideXlab platform.
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ASymmetric SyntheSiS of C-19 to C-27 fragment of Rifamycin-S
Tetrahedron Letters, 1995Co-Authors: Jhillu S. Yadav, C. Srinivas Rao, Srivari Chandrasekhar, A. V. Rama RaoAbstract:A highly StereoSelective aSymmetric SyntheSiS of C-19 to C-27 fragment of Rifamycin-S conSiSting of 7 contiguouS aSymmetric centreS iS deScribed involving Ipc2BH aS the chiral hydroborating reagent.
