351
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Ghosh AK, Pretzer E, Cho H, Hussain KA, Düzgüneş N. Antiviral activity of UIC-PI, a novel inhibitor of the human immunodeficiency virus type 1 protease. Antiviral Res 2002; 54:29-36. [PMID: 11888655 DOI: 10.1016/s0166-3542(01)00209-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The human immunodeficiency virus type 1 (HIV-1) protease inhibitor UIC-PI (1) was developed via structure-based design and incorporated a novel bis-tetrahydrofuran (bis-THF) ligand in the (R)-(hydroxyethyl)sulfonamide based isostere. The EC(50) and EC(90) of the compound in acutely-infected H9 cells were <1 and approximately 1 nM, respectively. In chronically infected H9/HIV-1(IIIB) cells, the EC(50) and EC(90) were 20 and 50 nM, respectively. In parallel studies comparing UIC-PI and saquinavir in H9/HIV-1(IIIB) cells, viral p24 levels in culture supernatants were an order of magnitude lower with UIC-PI than with saquinavir.
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352
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Gupta M, Hernon M, Gokhale R, Ghosh AK. Cost effectiveness analysis of a population based screening programme for asymptomatic Chlamydia trachomatis infection in women. Sex Transm Infect 2002; 78:76. [PMID: 11872877 PMCID: PMC1763685 DOI: 10.1136/sti.78.1.76-a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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353
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Yoshimura K, Kato R, Kavlick MF, Nguyen A, Maroun V, Maeda K, Hussain KA, Ghosh AK, Gulnik SV, Erickson JW, Mitsuya H. A potent human immunodeficiency virus type 1 protease inhibitor, UIC-94003 (TMC-126), and selection of a novel (A28S) mutation in the protease active site. J Virol 2002; 76:1349-58. [PMID: 11773409 PMCID: PMC135775 DOI: 10.1128/jvi.76.3.1349-1358.2002] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We identified UIC-94003, a nonpeptidic human immunodeficiency virus (HIV) protease inhibitor (PI), containing 3(R),3a(S),6a(R)-bis-tetrahydrofuranyl urethane (bis-THF) and a sulfonamide isostere, which is extremely potent against a wide spectrum of HIV (50% inhibitory concentration, 0.0003 to 0.0005 microM). UIC-94003 was also potent against multi-PI-resistant HIV-1 strains isolated from patients who had no response to any existing antiviral regimens after having received a variety of antiviral agents (50% inhibitory concentration, 0.0005 to 0.0055 microM). Upon selection of HIV-1 in the presence of UIC-94003, mutants carrying a novel active-site mutation, A28S, in the presence of L10F, M46I, I50V, A71V, and N88D appeared. Modeling analysis revealed that the close contact of UIC-94003 with the main chains of the protease active-site amino acids (Asp29 and Asp30) differed from that of other PIs and may be important for its potency and wide-spectrum activity against a variety of drug-resistant HIV-1 variants. Thus, introduction of inhibitor interactions with the main chains of key amino acids and seeking a unique inhibitor-enzyme contact profile should provide a framework for developing novel PIs for treating patients harboring multi-PI-resistant HIV-1.
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354
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Ghosh AK, Pani PK. Induced liver tumour further support to a genetic marker with its high correlation with chorioallantoic membrane phenotypes in selected layer lines. INDIAN JOURNAL OF EXPERIMENTAL BIOLOGY 2002; 40:144-50. [PMID: 12622176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
The conventional chorioallantoic membrane (CAM) phenotype assay was conducted using 11-day-old embryonatic eggs of white Leghorn strains, each inoculated with 0.2 ml of subgroup A Rous sarcoma virus (RSV) and subgroup C RSV separately containing 10(3)pfu ml(-1). Eggs were further incubated for hatching. Harvesting of CAMs for counting of pocks and monitoring chicks for liver tumour (LT) mortality during 4 weeks of post-hatching period were followed. The conversely associated phenotype (CAP) incidence i.e. CAM(+) LT(-) and CAM(-) LT(+) was observed in all three lines for both subgroup A and C virus infection. The LT deaths of chicks in all strains occurred within 21 days post-hatch irrespective of virus subgroups. The regression analysis of %LT death (transformed data) distributed within pock count range (PCR) basis was performed. The regression coefficients (b(i)'s) were found to be non-significant, indicating that %LT death did not correlate with number of particles that entered the cells because the chicks that had at least 25 pock counts in CAMs died with few exceptions. This study upheld the view that the CAM phenotypes (S and R) under the control of a pair of alleles, a(s) and a(r) at the tva locus and c(s) and c(r) at the tvc locus as reported extensively. Because of a high correlation coefficients between CAM and LT phenotypes [S and LT(+)] in respect of subgroup A (r = 0.72) and subgroup C (r = 0.81) infection, it is obvious that one could postulate a pleiotropic control of the two traits by the tva and tvc genes, respectively. Indeed fitting a 4-allele model in both tva and tvc locus, suggesting that CAPs are the indicator for nullifying the conventional 2-allele model proposed for the induced tumour expression phenotypes by leukosis sarcoma viruses.
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355
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Ghosh AK, Lei H. Stereoselective Synthesis of the C 11-N 26 Fragment of Griseoviridin. SYNTHESIS-STUTTGART 2002; 2002:371-374. [PMID: 30449904 DOI: 10.1055/s-2002-20037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The C11-N26 fragment of griseoviridin has been prepared enantioselectively. The 1,3-syn diol synthon was derived from lipase-catalyzed selective acylation of(±)-1-(benzyloxy)pent-4-en-2-ol. The conjugated (E,E)-dienylmethyl azide functionality was installed by a Pd-catalyzed allylic azidation reaction.
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356
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Ghosh AK, Shin D, Schiltz G. MULTICOMPONENT REACTIONS: SYNTHESIS OF SPIROCYCLIC TETRAHYDROPYRAN DERIVATIVES BY PRINS CYCLIZATION. HETEROCYCLES 2002; 58:659-666. [PMID: 30393424 PMCID: PMC6214194 DOI: 10.3987/com-02-s(m)63] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Substituted spirocyclic tetrahydropyranyl mesylates and tosylates have been synthesized in good yields using a Prins-type cyclization of various cyclic ketones, a homoallylic alcohol and either methanesulfonic or p-toluenesulfonic acid under non-aqueous conditions. The mesylates thus produced could then be transformed into the corresponding Boc-protected amines using an efficient two step procedure.
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357
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Abstract
An enantioselective first total synthesis of laulimalide (1) is described. Laulimalide, a remarkably potent antitumor macrolide, has been isolated from the Indonesian sponge Hyattella sp. and the Okinawan sponge Fasciospongia rimosa. Laulimalide represents a new class of antitumor agents with significant clinical potential. The synthesis is convergent and involved the assembly of C(3)-C(16) segment 4 and C(17)-C(28) segment 5 by Julia olefination. The sensitive C(2)-C(3) cis-olefin functionality was installed by Yamaguchi macrolactonization of a hydroxy alkynic acid followed by hydrogenation of the resulting alkynoic lactone over Lindlar's catalyst. Initial attempts of intramolecular Still's variant of Horner-Emmons olefination between the C(19)-phosphonocetate and C(3)-aldehyde provided a 1:2 mixture of cis- and trans-macrolactones. The trans-isomer was photoisomerized to a mixture of cis- and trans-isomers. The other key steps involved ring-closing olefin metathesis to construct both dihydropyran units, stereoselective anomeric alkylation to functionalize the dihydropyran ring, stereoselective reduction of the resulting alkynyl ketone to set the C(20)-hydroxyl stereochemistry, and a novel Julia olefination protocol for the installation of the C(13)-exo-methylene unit. The sensitive epoxide at C(16)-C(17) was introduced in a highly stereoselective manner by Sharpless epoxidation at the final stage of the synthesis.
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358
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Abstract
Ginkgolide A (1) has been synthesized from the trilactone 3 and also from ginkgolide B (2).
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359
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Mukherjee S, Ghosh AK, Sarkar S. Eosinophilic fasciitis. THE JOURNAL OF THE ASSOCIATION OF PHYSICIANS OF INDIA 2001; 49:1211-2. [PMID: 11996452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
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360
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361
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Ghosh AK, Ribolla PE, Jacobs-Lorena M. Targeting Plasmodium ligands on mosquito salivary glands and midgut with a phage display peptide library. Proc Natl Acad Sci U S A 2001; 98:13278-81. [PMID: 11687659 PMCID: PMC60861 DOI: 10.1073/pnas.241491198] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Despite vast efforts and expenditures in the past few decades, malaria continues to kill millions of persons every year, and new approaches for disease control are urgently needed. To complete its life cycle in the mosquito, Plasmodium, the causative agent of malaria, has to traverse the epithelia of the midgut and salivary glands. Although strong circumstantial evidence indicates that parasite interactions with the two organs are specific, hardly any information is available about the interacting molecules. By use of a phage display library, we identified a 12-aa peptide--salivary gland and midgut peptide 1 (SM1)--that binds to the distal lobes of the salivary gland and to the luminal side of the midgut epithelium, but not to the midgut surface facing the hemolymph or to ovaries. The coincidence of the tissues with which parasites and the SM1 peptide interact suggested that the parasite and peptide recognize the same surface ligand. In support of this hypothesis, the SM1 peptide strongly inhibited Plasmodium invasion of salivary gland and midgut epithelia. These experiments suggest a new strategy for the genetic manipulation of mosquito vectorial capacity.
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362
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Ghosh AK. Communications of adverse effects of medications: physician challenges and informatics readiness. ARCHIVES OF INTERNAL MEDICINE 2001; 161:2387. [PMID: 11606163 DOI: 10.1001/archinte.161.19.2387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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363
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Turner RT, Koelsch G, Hong L, Castanheira P, Ermolieff J, Ghosh AK, Tang J. Subsite Specificity of Memapsin 2 (β-Secretase): Implications for Inhibitor Design. Biochemistry 2001. [DOI: 10.1021/bi0151465] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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364
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Ghosh AK, Shin D, Swanson L, Krishnan K, Cho H, Hussain KA, Walters DE, Holland L, Buthod J. Structure-based design of non-peptide HIV protease inhibitors. ACTA ACUST UNITED AC 2001; 56:29-32. [PMID: 11347961 DOI: 10.1016/s0014-827x(01)01025-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A number of structurally novel P2-ligands have been designed and synthesized. Incorporation of these ligands in the (R)-(hydroxyethyl)sulfonamide isostere provided a series of potent non-peptidyl HIV protease inhibitors.
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365
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Ghosh AK, Shirai M. Asymmetric hetero Diels-Alder route to quaternary carbon centers: synthesis of (-)-malyngolide. Tetrahedron Lett 2001; 42:6231-6233. [PMID: 30393409 PMCID: PMC6214206 DOI: 10.1016/s0040-4039(01)01227-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Conformationally constrained chiral bis(oxazoline)-metal complex catalyzed asymmetric hetero Diels-Alder reactions of Danishefsky's diene and a variety of α-keto esters constructed quaternary carbon centers enantioselectively. The reaction was utilized in the synthesis of (-)-malyngolide.
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366
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Datta A, Ghosh AK, Kundu SC. Purification and characterization of fibroin from the tropical Saturniid silkworm, Antheraea mylitta. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2001; 31:1013-1018. [PMID: 11483437 DOI: 10.1016/s0965-1748(01)00049-2] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The fibroin protein isolated from the posterior silkgland of the tropical Saturniid silkworm Antheraea mylitta, was solubilized in lithium dodecyl sulfate and purified by gel filtration. The major fraction from gel filtration was analyzed by SDS-PAGE under non-reducing and reducing conditions. One major protein band of ca 395 kDa was obtained under non-reducing conditions and a doublet band of approximately 197 kDa under reducing conditions. The appearance of a single spot in two-dimensional electrophoresis confirmed the purity of the protein indicating that it may be a homodimeric protein of two similar sized polypeptides. Amino acid composition analysis showed that, like other Saturniid fibroins, it is rich in glycine, alanine and serine amino acids. N-terminal amino acid sequence shows significant homology with other Antheraea species. The enzymatic deglycosylation analysis indicates that the fibroin protein is glycosylated and the oligosaccharides are O-linked to the protein backbone by N-acetylgalactoseamine moiety which conforms to a Core 1 mucin-type glycosylation pattern.
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367
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Ghosh AK, Bilcer G, Harwood C, Kawahama R, Shin D, Hussain KA, Hong L, Loy JA, Nguyen C, Koelsch G, Ermolieff J, Tang J. Structure-based design: potent inhibitors of human brain memapsin 2 (beta-secretase). J Med Chem 2001; 44:2865-8. [PMID: 11520194 DOI: 10.1021/jm0101803] [Citation(s) in RCA: 197] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Memapsin 2 (beta-secretase) is one of two proteases that cleave the beta-amyloid precursor protein (APP) to produce the 40-42 residue amyloid-beta peptide (Abeta) in the human brain, a key event in the progression of Alzheimer's disease. On the basis of the X-ray crystal structure of our lead inhibitor (2, OM99-2 with eight residues) bound to memapsin, we have reduced the molecular weight and designed potent memapsin inhibitors. Structure-based design and preliminary structure-activity studies have been presented.
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368
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Turner RT, Koelsch G, Hong L, Castanheira P, Ermolieff J, Ghosh AK, Tang J, Castenheira P, Ghosh A. Subsite specificity of memapsin 2 (beta-secretase): implications for inhibitor design. Biochemistry 2001; 40:10001-6. [PMID: 11513577 DOI: 10.1021/bi015546s] [Citation(s) in RCA: 147] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Memapsin 2 is the protease known as beta-secretase whose action on beta-amyloid precursor protein leads to the production of the beta-amyloid (Abeta) peptide. Since the accumulation of Abeta in the brain is a key event in the pathogenesis of Alzheimer's disease, memapsin 2 is an important target for the design of inhibitory drugs. Here we describe the residue preference for the subsites of memapsin 2. The relative k(cat)/K(M) values of residues in each of the eight subsites were determined by the relative initial cleavage rates of substrate mixtures as quantified by MALDI-TOF mass spectrometry. We found that each subsite can accommodate multiple residues. The S(1) subsite is the most stringent, preferring residues in the order of Leu > Phe > Met > Tyr. The preferences of other subsites are the following: S(2), Asp > Asn > Met; S(3), Ile > Val > Leu; S(4), Glu > Gln > Asp; S(1)', Met > Glu > Gln > Ala; S(2)', Val > Ile > Ala; S(3)', Leu > Trp > Ala; S(4)', Asp > Glu > Trp. In general, S subsites are more specific than the S' subsites. A peptide comprising the eight most favored residues (Glu-Ile-Asp-Leu-Met-Val-Leu-Asp) was found to be hydrolyzed with the highest k(cat)/K(M) value so far observed for memapsin 2. Residue preferences at four subsites were also studied by binding of memapsin 2 to a combinatorial inhibitor library. From 10 tight binding inhibitors, the consensus preferences were as follows: S(2), Asp and Glu; S(3), Leu and Ile; S(2)', Val; and S(3)', Glu and Gln. An inhibitor, OM00-3, Glu-Leu-Asp-LeuAla-Val-Glu-Phe (where the asterisk represents the hydroxyethylene tansition-state isostere), designed from the consensus residues, was found to be the most potent inhibitor of memapsin 2 so far reported (K(i) of 3.1 x 10(-10) M). A molecular model of OM00-3 binding to memapsin 2 revealed critical improvement of the interactions between inhibitor side chains with enzyme over a previous inhibitor, OM99-2 [Ghosh, A. K., et al. (2000) J. Am. Chem. Soc. 14, 3522-3523].
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369
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Ghosh AK, Bischoff A, Cappiello J. Stereoselective synthesis of pseudopeptide microbial agent AI-77-B. Org Lett 2001; 3:2677-80. [PMID: 11506607 DOI: 10.1021/ol0101279] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[structure: see text]. An efficient and highly stereoselective synthesis of the gastroprotective natural product AI-77-B is described. The stereocenters of the hydroxy amino acid moiety were generated by an ester-derived titanium-enolate-mediated syn-aldol reaction, a Curtius rearrangement, and application of Dondoni's aldehyde homologation. Condensation with the dihydroisocoumarin fragment and subsequent deprotecting transformations furnished optically active AI-77-B.
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370
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Ghosh AK. Evidence-based diagnosis of severe aortic stenosis. QJM 2001; 94:397-8. [PMID: 11435636 DOI: 10.1093/qjmed/94.7.397-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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371
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Marinelli M, Ghosh AK, Mercuri F. Small quartz silica spheres induced disorder in octylcyanobiphenyl (8CB) liquid crystals: a thermal study. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:061713. [PMID: 11415129 DOI: 10.1103/physreve.63.061713] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2000] [Indexed: 05/23/2023]
Abstract
A photopyroelectric technique has been applied to the study of specific heat and thermal conductivity of homeotropically aligned mixtures of small quartz spheres (aerosil) and octylcyanobiphenyl (8CB) with concentration 0</=rho(s)</=0.04 g/cm(3). Thermal conductivity data show that, even at these very low concentrations, an annealing of the disorder introduced by the aerosil takes place on cooling at the smectic-A-nematic (Sm-A-N) phase transition and not only at the nematic-isotropic (N-I) one. This means that there is some elastic strain in the nematic phase of the sample which is not quenched. Accordingly the suppression of the N-I transition temperature as a function of rho(s) does not fit a random field with a random dilution model that accounts for random quenched disorder only. High resolution specific heat measurements at the A-N and N-I transition show the effect of the aerosil is not the same. While in the first case its peak is suppressed with increasing concentration, in the second case there are some indications that outside the two-phase coexistence region it is enhanced. The effect of surface-induced alignment is also discussed to explain some discrepancies between our data and the ones reported in literature. It is concluded that the amount of disorder in the sample does not depend on rho(s) only, but also on other variables such as external fields. Finally, a relaxation phenomenon in the aerosil network that partially compensate the disordering effect of the particles is suggested to explain the concentration dependence of the transition temperatures.
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372
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Ghosh AK, Wang Y. A macrolactonization-based strategy to obtain microtuble-stabilizing agent (-)-laulimalide. Tetrahedron Lett 2001; 42:3399-3401. [PMID: 30464359 PMCID: PMC6241315 DOI: 10.1016/s0040-4039(01)00436-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
An alternative synthesis of anti-tumor macrolide (-)-laulimalide is described. The synthesis was achieved utilizing Yamaguchi macrolactonization as the key step. The sensitive C2-C3 cis-olefin functionality has been installed by a macrolactonization of hydroxy alkynic acid and subsequent hydrogenation over Lindlar's catalyst.
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373
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Datta A, Ghosh AK, Kundu SC. Differential expression of the fibroin gene in developmental stages of silkworm, Antheraea mylitta (Saturniidae). Comp Biochem Physiol B Biochem Mol Biol 2001; 129:197-204. [PMID: 11337263 DOI: 10.1016/s1096-4959(01)00377-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Fibroin gene expression during the larval developmental stages of the Saturniid silkworm, Antheraea mylitta, was analyzed. Northern blot analysis of larval silk gland total RNA using the fibroin gene as a probe showed that fibroin is expressed in the intermoult stages and repressed during the moulting stages. Abundance of fibroin transcripts gradually increased from the third to fifth intermoult stage, reaching a peak in the fifth intermoult. Transcripts declined during the early spinning stage. Western blot analysis of fibroin protein production with anti-fibroin antibody confirmed the differential fibroin expression, in accordance with fibroin mRNA synthesis. Dot blot hybridization of genomic DNA isolated from each larval developmental stage with the labelled fibroin gene showed that at the genomic level, the relative concentration of the fibroin gene was constant throughout the developmental stages. Our data confirm that fibroin gene expression in A. mylitta, like in B. mori, is transcriptionally controlled and shows differential temporal variations.
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374
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Corey EJ, Rao KS, Ghosh AK. INTRAMOLECULAR AND INTERMOLECULAR HYDROXYL REACTIVITY DIFFERENCES IN GINKGOLIDES A, B AND C AND THEIR CHEMICAL APPLICATIONS. Tetrahedron Lett 2001; 33:6955-6958. [PMID: 30310244 DOI: 10.1016/s0040-4039(00)60905-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
An investigation of the chemistry of ginkgolides A, B and C (1) has revealed an unusual interaction between the hydroxyl groups at C(1) and C(10) which activates their deprotonation to give 2 and provides a method for the interconversion of 1C and 1B. The ginkgolide 7-enol system 7 is more stable than the corresponding 7-keto form 6, which is easily made by selective Jones oxidation of ginkgolide C.
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375
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Abstract
A new route to α-methylene lactones, important structural subunits of many natural products, has been developed using the nitrile oxide derived from 2-nitroethanol.
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