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S Spinelli

Publications and source records attributed to S Spinelli.

At least 55 records · Page 3Linked to original sources
PubMed1997

Structure of a pancreatic alpha-amylase bound to a substrate analogue at 2.03 A resolution.

The structure of pig pancreatic alpha-amylase in complex with carbohydrate inhibitor and proteinaceous inhibitors is known but the successive events occurring at the catalytic center still remain to be elucidated. The X-ray structure analysis of a crystal of pig pancreatic alpha-amylase (PPA, EC 3.2.1.1.) soaked with an enzyme-resistant substrate analogue, methyl 4,4'-dithio-alpha-maltotrioside, showed electron density corresponding to the binding of substrate analogue molecules at the active site and at the "second binding site." The electron density observed at the active site was interpreted in terms of overlapping networks of oligosaccharides, which show binding of substrate analogue molecules at subsites prior to and subsequent to the cleavage site. A weaker patch of density observed at subsite -1 (using a nomenclature where the site of hydrolysis is taken to be between subsites -1 and +1) was modeled with water molecules. Conformational changes take place upon substrate analogue binding and the "flexible loop" that constitutes the surface edge of the active site is observed in a specific conformation. This confirms that this loop plays an important role in the recognition and binding of the ligand. The crystal structure was refined at 2.03 A resolution, to an R-factor of 16.0 (Rfree, 18.5).

Acarbose↗
PubMed1997

Effects of UV and visible radiation on DNA-final base damage.

Several mechanisms are likely to be involved in the solar radiation-mediated modifications of cellular DNA. Direct excitation of DNA bases by the UVB component (290-320 nm) of solar light gives rise, mostly through oxygen independent reactions, to the formation of dimeric pyrimidine lesions including cyclobutadipyrimidines, pyrimidine (6-4) pyrimidone photoproducts and related valence Dewar isomers. In addition, photoexcitation of cytosine and guanine may lead to the formation in relatively minor yields of 6-hydroxy-5,6-dihydrocytosine and 8-oxo-7,8-dihydroguanine, respectively. A second mechanism that requires the participation of endogenous photosensitizers together with oxygen is at the origin of most of the DNA damage generated by the UVA (320-400 nm) and visible light. Singlet oxygen, which arises from a type II mechanism, is likely to be mostly involved in the formation of 8-oxo-7,8-dihydroguanine that was observed within both isolated and cellular DNA. However, it may be expected that the latter oxidized purine lesion together with DNA strand breaks and pyrimidine base oxidation products are also generated with a lower efficiency through Fenton type reactions. A more definitive assessment of these mechanisms would require further studies aimed at the identification and quantification of the different DNA photolesions including both dimeric pyrimidine photoproducts and photooxidized lesions.

Animals↗
PubMed1996

Crystallization and preliminary X-ray study of the 8-amino-7-oxopelargonate synthase from Bacillus sphaericus.

The 8-amino-7-oxopelargonate synthase (AOPS) cloned from Bacillus sphaericus, overproduced in Escherichia coli, has been crystallized in the pyridoxal 5'-phosphate (PLP)-bound form at pH 7.5, using polyethylene glycol as the precipitant. One crystal form corresponds to a tetragonal space group, with unit-cell dimensions a = b = 66, c = 181 A. These crystals do not diffract beyond 5 A, with conventional X-ray sources and cannot be used in the structure elucidation. A second crystal form is obtained when crystallization conditions are varied slightly by the addition of 0.2 M ammonium sulfate. The space group is P2(1)2(1)2(1), with unit-cell dimensions a = 68.9, b = 85.5, c = 125.9 A, indicating the presence of two molecules in the asymmetric unit (V(m) = 2.26 A(3) Da(-1); 46% water). These crystals diffract X-rays up to 3.2 A using in-house facilities and a preliminary data set has been collected. A second data set using the synchrotron radiation source W32 at LURE (Paris) has shown the crystals to diffract to at least 3 A, resolution, with good statistics. The structure determination of AOPS will provide a structural framework for the other alpha-amino ketone synthases for which no three-dimensional structure is yet available.

Journal Article↗
PubMed1996

Domain swapping creates a third putative combining site in bovine odorant binding protein dimer.

In mammals, odorant binding proteins may play an important role in the transport of odors towards specific olfactory receptors on sensory neurones across the aqueous compartment of the nasal mucus. We have solved the X-ray structure of such a transport protein, bovine odorant binding protein (OBP) at 2.0 A resolution. The beta-barrel of OBP is similar to that of lipocalins, but OBP dimer association results from domain swapping, an observation unique among the lipocalins. The alpha-helix of each monomer stacks against the beta-barrel of the other monomer. Contrary to previous reports, each monomer has an internal buried cavity which could accommodate a naturally occurring molecule. Besides this cavity, an open cavity is located at the dimer interface. Data in solution suggest that this central cavity may be a binding site created by domain swapping.

Animals↗
PubMed1996

Purified fusion protein vaccine protects against lower respiratory tract illness during respiratory syncytial virus season in children with cystic fibrosis.

OBJECTIVE: To test in a double blind, placebo-controlled study a purified fusion protein (PFP-2) vaccine against respiratory syncytial virus (RSV) in RSV-seropositive children with cystic fibrosis (CF). METHODS: Seventeen CF children, mean age 4.5 years, received PFP-2 vaccine and 17 CF children, mean age 5.8 years, received a saline vaccine. At enrollment the Shwachman clinical score, Brasfield radiographic score, oxygen saturation (SpO2), anthropometric indices and other variables were recorded. After vaccination the reactions were assessed daily for 7 days. During the RSV season weekly telephone interviews were performed and children with an acute respiratory illness were evaluated and cultured for RSV. Serum was drawn before vaccination, 1 month after vaccination and at the end of the RSV season and tested for antibodies to RSV. RESULTS: Other than age the baseline measurements at enrollment were similar between groups. The PFP-2 vaccine produced mild local reactions and induced a significant neutralizing antibody response in two-thirds of the vaccinees and a significant enzyme-linked immunosorbent assay-fusion glycoprotein antibody response in nearly all the PFP-2 vaccinees. Vaccine-enhanced disease was not observed in PFP-2 vaccines infected with RSV. Protection against RSV infection was not observed; however, a significant reduction (t test, P < 0.01) in mean number of lower respiratory tract illnesses (0.8 vs. 2.1), antibiotic courses (2.2 vs 4.5) and days ill (30.5 vs. 67) occurred among RSV-infected PFP-2 vaccinees. CONCLUSIONS: Efficacy of the PFP-2 vaccine against lower respiratory tract illness during the RSV season was shown in RSV-seropositive children with CF.

Child↗
PubMed1996

Determinants involved in regulating the proportion of edited apolipoprotein B RNAs.

Editing the apolipoprotein B (apoB) RNA involves deamination of cytidine by the catalytic subunit, APOBEC-1, as a component of an editosome. A tripartite sequence (editing motif) is essential for editosome assembly and site-specific editing. Current theory for the regulation of apoB RNA editing proposes that APOBEC-1 is rate limiting in cells and determines the proportion of edited apoB mRNAs. An evaluation of how the overexpression of APOBEC-1 increased the proportion of edited RNAs has led to the discovery of a paradox. McArdle cells edit a constant proportion of apoB RNA regardless of the total number of apoB RNAs expressed. Despite virtually identical editing motifs, apoB RNA transcripts from the endogenous gene and transfected, exogenous cDNA were edited with characteristic, but different efficiencies. This suggested that these RNAs were interacting with the editing machinery as distinct and noncompeting populations. We evaluated whether the presence of introns in the endogenous transcript may have distinguished it as a distinct population having reduced editing efficiency. The editing efficiency of chimeric splicing-editing RNA substrates was highest on fully processed RNA. Increased exon length improved utilization of the editing motif in these chimeric constructs. Taken together, the data suggest that the close proximity of introns can reduce apoB RNA editing efficiency. A population "gating" hypothesis is proposed wherein the proportion of edited RNAs in a population is determined my multiple cis- and trans-acting factors as RNAs pass through a nuclear restriction point.

APOBEC-1 Deaminase↗
PubMed1995

Multiple crystal forms of endoglucanase CelD: signal peptide residues modulate lattice formation.

The crystal structure of Clostridium thermocellum endoglucanase CelD revealed an extended NH2-terminal segment (involving residues from the putative leader peptide) sticking out from the enzyme core to interact with a symmetry related molecule through an intermolecular salt bridge (Lys38-Asp201). Enzymatic digestion of CelD with various proteases emphasized the flexibility of the NH2-segment in solution. Proteolytic removal of Lys38 or the substitution of bridge-forming residues by site-directed mutagenesis promoted crystal packing arrangements that differ from that of wild type CelD. Crystals of wild-type CelD (a = 99.3 A c = 191.8 A) are trigonal, space group P3(1)21, with one molecule in the asymmetric unit (form A), whereas crystals of papain-treated CelD (a = 100.4 A, c = 248.7 A), of CelDK38M (a = 100.1 A, c = 248.4 A) and of papain-treated CelDD201A (a = 99.9 A, c = 250.0 A) are trigonal, space group P3(1)21, with two crystallographically independent molecules (form B), and crystals of chymotrypsin-treated CelD (a = 100.0 A, c = 254.3 A) and of CelDD201A (a = 99.8 A, c = 254.7 A) are hexagonal, space group P6(1)22, with one molecule in the asymmetric unit (form C). Only chymotrypsin-treated CelD (which preserves both Lys38 and Asp201) can grow in crystal form A upon macroseeding, indicating that formation of the intermolecular salt bridge is critical for stability of this crystal form. Flexible NH2- and COOH-terminal peptide extensions were found to influence crystal nucleation, but not crystal growth. The crystal structures of papain-treated CelD and chymotrypsin-treated CelD, determined at 3.5 A resolution by molecular replacement techniques, demonstrate that a small change in molecular orientation promoted by Lys38 account for the differences between crystal forms B and C.

Amino Acid Sequence↗
PubMed1995

N-acyl-2-substituted-1,3-thiazolidines, a new class of non-narcotic antitussive agents: studies leading to the discovery of ethyl 2-[(2-methoxyphenoxy)methyl]-beta-oxothiazolidine-3-propanoate.

The synthesis of a novel class of antitussive agents is described. The compounds were examined for antitussive activity in guinea pig after cough induction by electrical or chemical stimulation. Ethyl 2-[(2-methoxyphenoxy)methyl]-beta-oxothiazolidine-3-propanoate (BBR 2173, moguisteine, 7) and other structurally related compounds showed a significant level of activity, comparable to that of codeine and dextromethorphan. The compounds presented in this paper are characterized by the N-acyl-2-substituted-1,3-thiazolidine moiety, which is a novel entry in the field of antitussive agents. The serendipitous discovery of the role played by the thiazolidine moiety in determining the antitussive effect promoted extensive investigations on these structures. This optimization process on N-acyl-2-substituted-1,3-thiazolidines led to the initial identification of 2-[(2-methoxypheoxy)methyl]-3-[2-(acetylthio)acetyl]- 1,3-thiazolidine (18a) as an interesting lead compound. The careful study of the rapid and very complicated metabolism of 18a provided further insights for the design of newer related derivatives. The observation that the metabolic oxidation on the lateral chain's sulfur of 18a to sulfoxide maintained the antitussive properties suggested the introduction of isosteric functional groups with respect to the sulfoxide moiety. Subsequent structural modifications showed that hydrolyzable malonic residues in the 3-position of the thiazolidine ring were able to assure high antitussive activity. This optimization ultimately led to the selection of moguisteine (7) as the most effective and safest representative of the series. Moguisteine is completely devoid of unwanted side effects (such as sedation and addiction), and its activity was demonstrated also in clinical studies.

Animals↗
PubMed1995

Chromophore-modified antitumor anthracenediones: synthesis, DNA binding, and cytotoxic activity of 1,4-bis[(aminoalkyl)amino]benzo[g]-phthalazine-5,10-diones.

As part of a program aimed at exploring the effect of the introduction of heteroatoms into the anthracene-9,10-dione chromophore, we have synthesized novel 1,4-bis[(aminoalkyl)amino]-benzo[g]phthalazine-5,10-diones (BPDs) 1 which are related to the antitumor agents ametantrone and mitoxantrone. Derivatives 1 were prepared by chromic acid oxidation of acylated benzo[g]phthalazines 5 followed by acid hydrolysis or by silylation-amination of 5,10-dihydroxybenzo[g]phthalazine-1,4-dione (8). The 1-[(aminoalkyl)amino]-4-amino congeners 2 were isolated in low yields as byproducts from the oxidation of 5. Against a panel of human tumor cell lines, the benzo[g]phthalazine-5,10-diones 1 and 2 exhibited cytotoxic activity comparable or even superior to that of mitoxantrone. In compounds 1, structure-activity relationships different than those operative in the carbocyclic series appeared to emerge. DNA-binding studies with the ametantrone-like compound 1c and its single-armed congener 2c indicated that the introduction of a 2,3-diaza subunit into the anthracene-9,10-dione chromophore reduces the affinity of the drug for DNA in comparison with ametantrone. On the other hand, the number of side-chain groups does not affect binding to a great extent. These findings seem to suggest mechanisms of cell death other than those induced by simple interaction of the 1,4-BPDs 1 and 2 with DNA.

Cell Survival↗
PubMed1995

A common protein fold and similar active site in two distinct families of beta-glycanases.

The structure of Clostridium thermocellum endoglucanase CelC, a member of the largest cellulase family (family A), has been determined at 2.15 A resolution. The protein folds into an (alpha/beta)8 barrel, with a deep active-site cleft generated by the insertion of a helical subdomain. The structure of the catalytic core of xylanase XynZ, which belongs to xylanase family F, has been determined at 1.4 A resolution. In spite of significant differences in substrate specificity and structure (including the absence of the helical subdomain), the general polypeptide folding pattern, architecture of the active site and catalytic mechanism of XynZ and CelC are similar, suggesting a common evolutionary origin.

Amino Acid Sequence↗
PubMed1995

Topoisomerase II DNA cleavage stimulation, DNA binding activity, cytotoxicity, and physico-chemical properties of 2-aza- and 2-aza-oxide-anthracenedione derivatives.

The cytotoxic activity of mitoxantrone and related anthracenediones has been ascribed to the ability of these compounds to interfere with DNA topoisomerase II function, resulting in DNA cleavage stimulation. The molecular details of enzyme inhibition by these intercalating agents remain to be defined. In an attempt to identify the structural determinants for optimal activity, the molecular and cellular effects of a series of heteroanalogues bearing different side-chains were examined in relation to the physico-chemical and DNA binding properties of these compounds. The results indicated that substitution of a pyridine ring for the dihydroxyphenylene ring in the planar chromophore caused a marked reduction of cytotoxic activity and of the ability to stimulate topoisomerase II-mediated DNA damage in intact cells and with simian virus 40 DNA in vitro. Although all tested derivatives were shown to intercalate into DNA, their DNA binding affinities were appreciably lower than that of mitoxantrone. The behavior of 2-aza derivatives more closely resembled that of ametantrone, suggesting that the potency of agents of this class is influenced more by the presence of hydroxyl groups than by the phenylene ring. The observation that a dramatic reduction (or loss) of the ability of aza derivatives to stimulate DNA cleavage is associated with a marked reduction of cytotoxic potency supports a primary role of topoisomerase II-mediated effects in the mechanism of action of the effective agents of this class. Because appreciable cytotoxic activity and significant in vivo antitumor efficacy are retained by compounds inactive (or poorly active) in inhibition of topoisomerase II, these results are consistent with multiple effects of anthracenediones at the cellular level.

Antineoplastic Agents↗
PubMed1995

Aza and diaza bioisosteric anthracene-9,10-diones as antitumor agents.

Synthetic routes to aza and diaza bioisosteres related to the anthracene-9,10-dione, mitoxantrone, have been developed. The antitumor properties of these chemotypes are compared with those exhibited by the corresponding carbocyclic analogues. The sensitivity of the expressed cytotoxicities on the position(s) of the nitrogen atom(s) are discussed in terms of potential cellular targets. Several analogues show potential for clinical evaluations.

Animals↗
PubMed1994

Synthesis and antitumor activity of a new class of pyrazolo[4,3-e]pyrrolo[1,2-a][1,4]diazepinone analogues of pyrrolo[1,4][2,1-c]benzodiazepines.

A new class of pyrrolo[1,4]benzodiazepine (PBD) analogues featuring a pyrazolo[4,3-e]pyrrolo[1,2-a][1,4]diazepinone ring system has been designed and synthesized. These compounds, 2a-o, are characterized by the substitution of the aromatic A ring, characteristic of the PBDs, with a disubstituted pyrazole ring bearing alkyl and benzyl substituents at N6 or N7 and alkyl or carbomethoxy substituents at C8. Biological evaluation revealed an appreciable in vitro cytotoxic activity for compounds 2a,b,f-i.

Animals↗
PubMed1994

Crystallization and preliminary diffraction analysis of the catalytic domain of xylanase Z from Clostridium thermocellum.

The catalytic domain of a thermostable xylanase from Clostridium thermocellum has been expressed in Escherichia coli and crystallized from a polyethylene glycol 2000 solution by the hanging drop method. Crystals belong to the triclinic space group P1 with cell dimensions a = 46.8 A, b = 50.8 A, c = 70.3 A, alpha = 100.7 degrees, beta = 83.8 degrees, gamma = 101.6 degrees, and two molecules in the unit cell. These crystals diffract X-rays to at least 1.8 A resolution and are suitable for high-resolution X-ray analysis.

Amino Acid Sequence↗
PubMed1994

Ovarian recovery after total body irradiation and allogeneic bone marrow transplantation: long-term follow up of 79 females.

Seventy-nine females undergoing allogeneic BMT following conditioning with total body irradiation (TBI), were prospectively followed between March 1983 and March 1992 with regular gynaecological examinations, including plasma levels of luteinising hormone (LH), follicle stimulating hormone (FSH), 17-beta oestradiol (E2) and pelvic ultrasonography. The end-points of this study were the following: (1) early and late effects of TBI on ovarian function, (2) compliance and results of hormonal replacement therapy (HRT), and (3) predictive events for ovarian recovery. During the first year post-BMT most adult women complained of vasomotor and/or genitourinary tract symptoms. These were associated with decreased E2 and increased LH-FSH plasma levels and a deterioration in their sexual life (94% of sexually active women). Forty-nine adult females were selected to receive systemic hormonal replacement therapy (HRT), consisting of cyclic transdermal oestrogens plus medroxyprogesterone acetate (MPA) or cyclic oral therapy with low doses of conjugated oestrogens and MPA: these patients were selected on the basis of age (< 45 years), absence of medical contraindications or subjective refusal. Compliance and tolerability were overall good: most women (65%) never stopped HRT; this was discontinued in 14 patients for medical reasons and in 3 because of refusal. Forty-three females completed 6 months of HRT: vasomotor symptoms disappeared in 91% of 58 women who previously referred these symptoms. Improvement of genitourinary symptoms was seen both with local and systemic hormonal therapy. However sexual symptoms were reduced in 21 of 26 women (81%) given HRT compared with 8 of 19 (42%) women given local treatment (p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Monoclonal Ig L chain and L chain V domain fragment crystallization in myeloma-associated Fanconi's syndrome.

Monoclonal free L chains secreted in immunoproliferative disorders are frequently involved in renal complications, including a specific proximal tubule impairment, the Fanconi's syndrome, which is generally featured by intracellular crystallization of L chain-related material. In a patient with myeloma-associated Fanconi's syndrome, hexagonal crystals (most surrounded by smooth membranes) were found in kidney proximal tubular cells and bone marrow plasma cells and phagocytes. The sequence of the patient's monoclonal kappa-chain was deduced from that of identical kappa-cDNA clones from the tumoral plasma cells. Small protein-enriched gel filtration fractions from urine yielded crystals morphologically similar and with the same 60 A periodicity on electron micrographs as those found in the cells. N-terminal sequencing and mass spectrometry studies showed that the crystals contained a 107-amino acid fragment (with a C-terminal lysine) corresponding to the V domain together with a low proportion of the entire kappa-chain. In vitro trypsin and pepsin treatment of the native entire kappa-chain yielded a homogeneous V domain fragment which, contrary to other monoclonal kappa-chains, was completely resistant to further proteolytic attack. The patient's kappa-chain also displayed an unusual self-reactivity, as demonstrated by a Western blot technique. The peculiar proneness of the V domain to resist proteolysis and to form crystals might prevent the normal cell catabolism of the L chain and lead to crystallization and renal impairment.

Adult↗