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Biomedical subjects

G Valle

Publications and source records attributed to G Valle.

At least 73 records · Page 4Linked to original sources
PubMed1993

First characterization at atomic resolution of the C-activating groups in a peptide synthesis acid chloride, acid azide and carboxylic-carboxylic mixed anhydride.

The X-ray diffraction structures of three N alpha-protected, C alpha-activated MeAib derivatives are reported. They are Tos-MeAib-Cl, Tos-MeAib-N3 and Tos-MeAib-O-Piv. The geometry and conformation of these classical carboxyl activating groups, which have been characterized at atomic resolution for the first time, are discussed.

Anhydrides↗
PubMed1993

Conformational versatility of the N alpha-acylated tripeptide amide tail of oxytocin. Synthesis and crystallographic characterization of three C2 alpha-backbone modified, conformationally restricted analogues.

The synthesis, physical and analytical characterization, and crystal-state structural analysis by X-ray diffraction of three analogues of the N alpha-acylated tripeptide amide tail of oxytocin, each containing a cyclic C alpha, alpha-disubstituted glycine at position 2, have been performed. The peptides are Boc-L-Pro-Ac3c-Gly-NH2, Z-L-Pro-Ac5c-Gly-NH2 and Z-L-Pro-Ac6c-Gly-NH2. While the former is folded in a type-II beta-turn conformation at the -L-Pro-Ac3c- sequence, the two latter tripeptides form two consecutive (type-II, type-I') beta-turns. The Ac5c- and Ac6c-tripeptides are the first examples of such a highly folded structural combination in a position-2 analogue of the N alpha-acylated -L-Pro-L-Leu-Gly-NH2 sequence.

Acylation↗
PubMed1993

The beta-bend ribbon spiral. Synthesis and conformational analysis in solution and in the crystal state of depsipeptides containing alpha-hydroxyisobutyric acid.

The synthesis and conformational analysis in solution (by FTIR absorption and 1H NMR) and in the crystal state (by X-ray diffraction) of three Hib-containing depsipeptides have been performed. In the crystal state Z-Aib-Hib-Aib-OMe is folded into a type-III beta-bend, while the conformation adopted by Z-Aib-Hib)2-Aib-OMe is a beta-bend ribbon spiral, characterized by two type-III beta-bends with Aib(1)-Hib(2) and Aib(3)-Hib(4) as corner residues, respectively. Both independent molecules in the asymmetric unit of t-Boc-L-Ala-Hib-L-Ala-OMe crystals are folded into a type-II beta-bend. For the Aib-Hib depsipeptides the conformation adopted in the crystal state is also that largely prevailing in solution, whereas for t-Boc-L-Ala-Hib-L-Ala-OMe the beta-bend conformation is significantly less populated in solution. A comparison is also made with: (i) the published crystal-state conformations of fully protected -(Aib)3-, -(Aib)5-, and -L-Ala-Aib-L-Ala- sequences and the beta-bend ribbon spiral generated by (Aib-L-Pro)n oligomers, and (ii) with the herewith described solution preferred conformation of Z-L-Ala-Aib-L-Ala-OMe. The possible use of Hib as an isosteric replacement for Aib in the design of conformationally constrained depsipeptides is briefly discussed.

Amino Acid Sequence↗
PubMed1992

A putative serine/threonine protein kinase gene on chromosome III of Saccharomyces cerevisiae.

We have sequenced a gene on chromosome III of Saccharomyces cerevisiae which codes for a putative serine/threonine protein kinase of 726 amino acids (calculated molecular weight 82 kDa). We have called this gene KIN82. The amino acid sequence of KIN82 is most similar to the cyclic nucleotide-dependent protein kinase subfamily and the protein kinase C subfamily. Gene disruption of KIN82 did not produce any phenotype when tested under a variety of conditions. Reduced stringency hybridizations revealed the presence of another genomic sequence with high homology to the carboxy-terminal catalytic domain of KIN82.

Amino Acid Sequence↗
PubMed1992

Monomer units for the beta-bend ribbon structure: MeAib peptides.

A conformational analysis in CDCl3 solution by using i.r. absorption and 1H nuclear magnetic resonance spectroscopy was performed on the fully blocked dipeptides Z-MeAib-Aib-NHMe, Z-MeAib-L-Ala-NHMe, Z-Aib-MeAib-NHMe, and Z-L-Ala-MeAib-NHMe, representing repeating units of the beta-bend ribbon spiral (an approximate 3(10)-helix, with an intramolecular H-bonding donor every two residues), where Z represents benzyloxycarbonyl, MeAib alpha-methylaminoisobutyric acid, and NHMe methylamino. The molecular and crystal structures of the first three compounds were also assessed by X-ray diffraction. While the -MeAib-Aib-, -MeAib-L-Ala-, and -Aib-MeAib- sequences give stable beta-bend structures, the preferred conformation of the -L-Ala-MeAib- sequence is open. These results indicate that the MeAib residue is a good beta-bend promoter, but less efficient than its unmethylated counterpart at position i + 2.

Dipeptides↗
PubMed1992

Crossed cerebello-cerebral diaschisis: a SPECT study.

A scintigraphic single photon emission computed tomographic (SPECT) evaluation of frontal perfusion alteration was performed in five patients with known cerebellar lesions but with normal supratentorial computed tomographic (CT) or magnetic resonance (MR) scans. A clearly evident asymmetry was found in prefrontal areas in the four subjects with acquired cerebellar damage. The fifth subject, who had congenital left cerebellar hypoplasia, did not show any frontal flow asymmetry. The data support the growing clinical evidence that the cerebellum contributes to the cognitive processes of the frontal lobes and suggest a possible role for SPECT examination in the assessment of functional cognitive impairment in patients with acquired cerebellar lesions.

Adolescent↗
PubMed1992

[Recurrent cardiac echinococcosis: a report of a case with multiple intrapericardial cysts].

A case of an isolated recurrent cardiac hydatidosis with multiple intrapericardial cysts is presented. The patient, who underwent 2 previous surgical resection of intramyocardial and pericardial hydatid cysts, presented with atypical chest pain. The ECG and the perfusion scintigraphy with 201-thallium showed a previous lateral myocardial infarction. The diagnosis of recurrent cardiac hydatidosis was made by two-dimensional echocardiography and computed tomography and was confirmed by clinical and biochemical findings.

Adult↗
PubMed1991

Preferred conformation of peptides from C alpha,alpha- symmetrically disubstituted glycines: aromatic residues.

The conformational preference of C(alpha,alpha-diphenylglycine (D-phi-g) and C(alpha,alpha)-dibenzylglycine (Dbz) residues was assessed in selected derivatives and small peptides by conformational energy computations, ir absorption, 1H-nmr, and x-ray diffraction. Conformational energy computations on the two monopeptides strongly support the view that these C(alpha,alpha)-symmetrically disubstituted glycines are conformationally restricted and that their minimum energy conformation falls in the fully extended (C5) region. The results of the theoretical analyses appear to be in agreement with the solution and crystal-state structural propensities of three derivatives and seven di- and tripeptides.

Amino Acid Sequence↗
PubMed1991

The sequence of a 6.3 kb segment of yeast chromosome III reveals an open reading frame coding for a putative mismatch binding protein.

We report the sequence of a 6.3 kb segment of DNA mapping near the end of the right arm of chromosome III of Saccharomyces cerevisiae. The sequence reveals a major open reading frame coding for a putative protein of 1047 amino acids with a striking similarity to the bacterial proteins involved in recognition of mismatched DNA base pairs. This is particularly interesting as the existence of a yeast mismatch repair system similar to that of bacteria has been postulated for some years, but a yeast protein homologous to the bacterial mismatch binding protein had not been identified. The results of a comparison of the putative yeast mismatch binding protein with the bacterial mismatch binding proteins and with two cognate mammalian sequences, support the idea that a similar mismatch repair system may be present also in mammalian cells. The possibility that all of these proteins may have evolved from a common ancestral gene is also discussed.

Amino Acid Sequence↗
PubMed1991

Different globin messenger RNAs are present before and after the metamorphosis in Lampetra zanandreai.

Lampreys are very primitive vertebrates belonging to the Agnata group. Although higher vertebrates have polymeric hemoglobin molecules which are encoded by several differentially expressed genes, lampreys have monomeric hemoglobins. However, it is unclear whether one or more globin genes are present. In this paper we show that four different species of globin can be separated by electrophoresis in acetic acid-urea-Triton gels. Two of the four species are present only before metamorphosis, while the other two are present only during adult life. In order to discover whether these differences are due to post-translational modifications of a unique amino acid sequence, we extracted globin mRNAs from both larval and adult stages and translated them in vitro. We found that both larval and adult globin mRNAs produce single globin bands; however, larval and adult bands are different from each other. Our data are consistent with the idea that two different globin genes are present in lampreys and that they are differentially expressed during development.

Animals↗
PubMed1991

Stereochemistry of peptides containing 1-aminocycloheptane-1-carboxylic acid (Ac7c).

The crystal structures of four peptides incorporating 1-aminocycloheptane-1-carboxylic acid (Ac7c) are described. Boc-Aib-Ac7c-NHMe and Boc-Pro-Ac7c-Ala-OMe adopt beta-turn conformations stabilized by an intramolecular 4----1 hydrogen bond, the former folding into a type-I/III beta-turn and the latter into a type-II beta-turn. In the dipeptide esters, Boc-Aib-Ac7c-OMe and Boc-Pro-Ac7c-OMe, the Ac7c and Aib residues adopt helical conformations, while the Pro residue remains semi-extended in both the molecules of Boc-Pro-Ac7c-OMe found in the asymmetric unit. The cycloheptane ring of Ac7c residues adopts a twist-chair conformation in all the peptides studied. 1H-NMR studies in CDCl3 and (CD3)2SO and IR studies in CDCl3 suggest that Boc-Aib-Ac7c-NHMe and Boc-Pro-Ac7c-Ala-OMe maintain the beta-turn conformations in solution.

Amino Acid Sequence↗
PubMed1991

Mass poisoning by sodium arsenite.

An acute massive epidemic of arsenic poisoning in Argentina involved 718 subjects. Urine samples were obtained from 307. The 49 with urine arsenic 76-500 micrograms/dl and 12 with urine arsenic greater than 500 micrograms/dL received dimercaprol treatment. Symptomatology increased with the urine arsenic with increased diarrhea, vomiting and systemic symptoms at urine arsenic greater than 75 micrograms/dL.

Adolescent↗
PubMed1991

Peptides from chiral C alpha,alpha-disubstituted glycines. Crystallographic characterization of conformation of C alpha-methyl, C alpha-isopropylglycine [(alpha Me)Val] in simple derivatives and model peptides.

The molecular and crystal structures of one derivative and three model peptides (to the pentapeptide level) of the chiral C alpha,alpha-disubstituted glycine C alpha-methyl, C alpha-isopropylglycine [(alpha Me)Val] have been determined by X-ray diffraction. The derivative is mClAc-L-(alpha Me)Val-OH, and the peptides are Z-L-(alpha Me)Val-(L-Ala)2-OMe monohydrate, Z-Aib-L-(alpha Me)Val-(Aib)2-OtBu, and Ac-(Aib)2-L-(alpha Me)Val-(Aib)2OtBu acetonitrile solvate. The tripeptide adopts a type-I beta-turn conformation stabilized by a 1----4N--H...O = C intramolecular H-bond. The tetra- and pentapeptides are folded in regular right-handed 3(10)-helices. All four L-(alpha Me)Val residues prefer phi, psi angles in the right-handed helical region of the conformational map. The results indicate that: (i) the (alpha Me)Val residue is a strong type-I/III beta-turn and helix former, and (ii) the relationship between (alpha Me)Val chirality and helix screw sense is the same as that of C alpha-monosubstituted protein amino-acids. The implications for the use of the (alpha Me)Val residue in designing conformationally constrained analogues of bioactive peptides are briefly discussed.

Amino Acid Sequence↗
PubMed1990

[Diagnosis of recent posterolateral myocardial infarction: an electrocardiographic, echocardiographic and scintigraphic study].

ECG and 2D echocardiography were studied in 64 patients with previous myocardial infarction and evidence of posterolateral fixed defect at 201 TI scintigraphy. The defect was isolated posterolateral in 47 patients (group 1), and posterolateral + inferoapical in 17 (group 2). Thirty subjects with no history of myocardial infarction and no 201 TI defects constituted the control group. We calculated sensitivity, specificity and predictive value of ECG and 2D echocardiography (pertinent wall motion abnormality) in the recognition of posterolateral infarction. ECG data were also analyzed using multivariate analysis. Among the ECG criteria, a positive T wave in V1 proved to be 100% sensitive and 76% specific both in group 1 and in group 2. At multivariate analysis, a 2-variable model (positive T wave inV1 + R/S ratio greater than or equal to 1 in V1-V2) had a sensitivity of 95 and 100% in group 1 and 2, respectively; the specificity was 80%. A 3-variable model (+ R wave duration in V1-V2 greater than or equal to 0.04 sec) proved to be less sensitive (70 and 88% in group 1 and 2, respectively), with a specificity of 97%. A pertinent dyssynergy at 2D echocardiography was 70% sensitive for posterolateral myocardial infarction in group 1, but only 29% in group 2, with a specificity of 100%. These results indicate: 1) standard ECG is more sensitive but less specific than 2D echocardiography in the recognition of previous postolateral myocardial infarction; 2) the recognition of posterolateral involvement can be frequently missed by 2D echocardiography in patients with associated inferior myocardial infarction.

Adult↗
PubMed1990

Hypoechoic focal liver lesions in granulomatous hepatitis and hemochromatosis.

Hypoechoic focal liver lesions are described, for the first time, in two patients with granulomatous hepatitis and hemochromatosis, and presenting a 'bright liver pattern' at ultrasonography. CT-scan was not able to make evident such areas in both cases, while hepatoscintigraphy revealed them only in the patient with granulomatous hepatitis. Echoguided fine-needle biopsies on the focal lesions were suitable for the correct final diagnoses. The finding of such areas was probably due to different intensity of the diseases in contiguous zones of liver parenchyma.

Adult↗
PubMed1989

Structure of (3S)-3-tert-butyloxycarbonylamino-2-piperidone.

C10H18N2O3, Mr = 214.27, monoclinic, P2(1), a = 15.515 (2), b = 6.730 (1), c = 12.541 (2) A, beta = 113.6 (2) degrees, V = 1200.0 A3, Z = 4, Dx = 1.186 g cm-3, lambda(Mo K alpha) = 0.71069 A, mu = 0.54 cm-1, F(000) = 464, T = 295 K. The final R value for 1611 observed (3139 unique) reflections is 0.055. In both the independent molecules A and B of the asymmetric unit of the title compound, the conformation of the urethane moiety is trans. The lactam group of molecule A is non-planar, the C(9)-N(2)-C(10)-C(6) torsion angle being 12.4 (14) degrees. One main difference between molecules A and B is in the value of the phi[C(5)-N(1)-C(6)-C(10)] torsion angle [52.3 (11) degrees for molecule A while -86.5 (10) degrees for molecule B] as a consequence of a rotation of the ring relative to the tert-butyloxycarbonylamino substituent. A second major difference is the delta-lactam ring conformation which is approximate half-chair for molecule A while boat for molecule B.

Chemical Phenomena↗