Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 23
Filtrar
1.
Chem Sci ; 13(45): 13563-13573, 2022 Nov 23.
Artículo en Inglés | MEDLINE | ID: mdl-36507175

RESUMEN

Humans are estimated to consume several grams per week of nanoplastics (NPs) through exposure to a variety of contamination sources. Nonetheless, the effects of these polymeric particles on living systems are still mostly unknown. Here, by means of CD, NMR and TEM analyses, we describe at an atomic resolution the interaction of ubiquitin with polystyrene NPs (PS-NPs), showing how a hard protein corona is formed. Moreover, we report that in human HeLa cells exposure to PS-NPs leads to a sensible reduction of ubiquitination. Our study overall indicates that PS-NPs cause significant structural effects on ubiquitin, thereby influencing one of the key metabolic processes at the base of cell viability.

2.
Am J Clin Nutr ; 48(2): 255-9, 1988 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-2841839

RESUMEN

The aim of this study was to compare the metabolic effects of a high-carbohydrate (CHO), high-fiber diet with only moderate protein restriction with those of a low-CHO, low-fiber diet with a low protein content in six diabetic patients with moderate chronic renal failure. The high-CHO, high-fiber diet induced a significant improvement in blood glucose control, a significant decrease in serum cholesterol, and a significant increase in fecal nitrogen losses. Other variables evaluated were not significantly different between the two diets, except for a significant increase in serum phosphorus during the high-CHO, high-fiber diet. N balance was not significantly different from 0 at the end of either dietary period and was very similar for both diets. The high-CHO, high-fiber diet presents many beneficial metabolic effects in diabetic patients with chronic renal failure.


Asunto(s)
Nefropatías Diabéticas/metabolismo , Carbohidratos de la Dieta/administración & dosificación , Fibras de la Dieta/administración & dosificación , Fallo Renal Crónico/metabolismo , Adulto , Glucemia/metabolismo , Colesterol/sangre , Creatinina/sangre , Diabetes Mellitus Tipo 1/metabolismo , Proteínas en la Dieta/administración & dosificación , Heces/análisis , Humanos , Nitrógeno/análisis , Fósforo/sangre , Albúmina Sérica/análisis
3.
Int J Vitam Nutr Res ; 58(3): 343-50, 1988.
Artículo en Inglés | MEDLINE | ID: mdl-3198323

RESUMEN

Several studies have investigated the relationship between obesity and mortality or cardiovascular disease (CVD) reporting conflicting results. The very few data collected on extremely obese patients have shown an increased mortality in these patients compared to the general population. Two hundred and sixtyfour (182 f, 82 m) severely obese patients (BMI greater than or equal to 35 w/h2) living in Southern Italy (hospitalized from 1972 to 1985 in our Metabolic Unit for a weight reduction program) were followed-up for a mean period of 7.1 years. Twentynine (20f, 9m) deaths were recorded during the follow-up. Higher mortality was found at all ages and in both sexes in these patients when compared to the general italian population. The excess mortality reached its peak in the age range 25-54 yrs (observed/expected mortality rate was 6.9 in females and 4.32 in males) diminishing by aging in both sexes (3.52 in females and 1.56 in males in age range 55-72 yrs). Death from CV disease was found more frequent than in the general italian population but it was unable to fully explain the excess mortality. Predictive factors of mortality were: in females age, BMI, and serum glucose and in males only age. In conclusion severely obese patients living in Southern Italy have a very high mortality rate. The excess mortality is not fully explained by cardiovascular disease.


Asunto(s)
Obesidad/mortalidad , Análisis Actuarial , Adolescente , Adulto , Factores de Edad , Anciano , Enfermedades Cardiovasculares/mortalidad , Femenino , Humanos , Masculino , Persona de Mediana Edad , Obesidad/complicaciones , Factores de Riesgo , Factores Sexuales , Pérdida de Peso
4.
Int J Vitam Nutr Res ; 58(2): 236-40, 1988.
Artículo en Inglés | MEDLINE | ID: mdl-3170099

RESUMEN

Aim of this study was to evaluate whether the age of onset of obesity might affect the prevalence of CV risk factors in severely obese patients. Five hundred forty-five (385 F aged 42.3 +/- 7.1 yrs, BMI 47.3 +/- 5.1 w/h2 and 160 M of 39.0 +/- 1.1 yrs and BMI of 41.8 +/- 5.3 w/h2) severely obese patients hospitalized in the Metabolic Unit between 1972 and 1985 were subdivided in four classes according to the age of onset of obesity. Severely obese women with maturity onset obesity (i.e. onset greater than or equal to 20 yrs) (MOO) had higher (p less than or equal to .01) serum glucose (118 vs 103 mg/dl) and triglyceride (167 vs 126 mg/dl) than those with early onset obesity (EOO) (i.e. onset less than or equal to 3 yrs) with the same age, BMI and smoking habits. Similar trend was also found in men. In males arterial blood pressure was found to be higher (p less than or equal to .01) in EOO than in MOO (SBP = 152 vs 133 mmHg and DBP = 92 vs 83 mmHg). Similar trend was found in females. In conclusion age of onset of obesity may, at least in part, affect the prevalence of cardiovascular risk factors in severe obesity.


Asunto(s)
Enfermedades Cardiovasculares/etiología , Obesidad/complicaciones , Adulto , Factores de Edad , Enfermedades Cardiovasculares/diagnóstico , Diabetes Mellitus , Femenino , Humanos , Hipercolesterolemia/etiología , Hiperlipoproteinemia Tipo IV/etiología , Hipertensión/etiología , Masculino , Persona de Mediana Edad , Factores de Riesgo
8.
J Pept Res ; 65(2): 200-8, 2005 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-15705164

RESUMEN

The Antennapedia homeodomain structure consists of four helices. The helices II and III are connected by a tripeptide that forms a turn, and constitute the well-known helix-turn-helix motif. The recognition helix penetrates the DNA major groove, gives specific protein-DNA contacts and forms direct, or water-mediated, intermolecular hydrogen bonds. It was suggested that helix III (and perhaps also helix IV) might represent the recognition helix of Antennapedia homeodomain, which makes contact with the surface of the major groove of the DNA. In an attempt to clarify the helix III capabilities of assuming an helical conformation when separated from the rest of the protein, we carried out the structural determination of the recognition helix III in different solvent media. The conformational study of fragments 42-53, where residues W48 and F49, not involved in the protein-DNA interaction, were substituted by two alanines, was conducted in sodium dodecyl sulfate (SDS), trifluoroethanol (TFE) and TFE/water, using circular dichroism, nuclear magnetic resonance (NMR) and distance geometry (DG) techniques. The fragment assumes a well-defined secondary structure in TFE and in TFE/water (90/10, v/v) with an alpha-helix encompassing residues 4-9, while in TFE/water (70/30, v/v) a less regular structure was found. The DG results in the micellar system evidence the presence of a distorted alpha-helical conformation involving residues 4-8. Our results reveal that the isolated Antennapedia recognition helix III tend to preserve in solution the alpha-helical conformation even if separated from the rest of the molecule.


Asunto(s)
Proteínas de Homeodominio/química , Proteínas Nucleares/química , Péptidos/química , Factores de Transcripción/química , Animales , Proteína con Homeodominio Antennapedia , Espectroscopía de Resonancia Magnética , Estructura Secundaria de Proteína , Solventes/química , Trifluoroetanol/química
9.
J Pept Sci ; 2(1): 3-13, 1996.
Artículo en Inglés | MEDLINE | ID: mdl-9225241

RESUMEN

The evaluation of peptide structures in solution is made feasible by the combined use of two-dimensional NMR in the laboratory (NOESY) and rotating frames (ROESY), and by the use of molecular dynamics calculations. The present paper describes how both the NMR method and molecular dynamics calculations were applied to very rigid synthetic bicycle peptides that are analogues of natural amatoxins. The NMR theory, which allows the estimate of interatomic distances between interacting nuclei, is briefly discussed. The experimental data were compared with those of known solid-state structures. Three amatoxin analogues have been examined. Of these, one is biologically active (S-deoxo gamma[R] OH-Ile3-amaninamide) and its structure in the solid state has recently been worked out. The second and third analogues (S-dexo-Ile3-Ala5-amaninamide and S-deoxo-D-Ile3-amaninamide, respectively) are inactive and their solid-state structures are unknown. The data presented confirm the authors previous hypothesis that lack of biological activity of S-deoxo-Ile3-Ala5-amaninamide is due to the masking of the tryptophan ring by the methyl group of L-Ala and not to massive conformational changes of the analogue.


Asunto(s)
Amanitinas/química , Compuestos Bicíclicos con Puentes/química , Péptidos/química , Espectrofotometría/métodos , Aminoácidos/análisis , Inhibidores Enzimáticos/química , Espectroscopía de Resonancia Magnética , Modelos Químicos , Conformación Proteica , Soluciones
10.
Int J Pept Protein Res ; 43(1): 47-61, 1994 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-8138351

RESUMEN

Synthesis and conformational analysis of three cyclic hexapeptides cyclo(-Gly1-Pro2-Phe3-Val4-Xaa5-Phe6), Xaa = Phe (I), D-Phe (II) and D-Pro (III), were carried out to examine the influence of proline on the formation of reverse turns and the dynamics of hydrophobic peptide regions. Assignment of all 1H and 13C resonances was achieved by homo- and heteronuclear 2D-NMR techniques (TOCSY, ROESY, HMQC, HMQC-TOCSY and HMBCS-270). The conformational analysis is based on interproton distances derived from ROESY spectra and homo- and heteronuclear coupling constants (E.COSY, HETLOC and HMBCS-270). For structural refinements restrained molecular dynamics (MD) simulations in vacuo and in DMSO were performed. Each peptide exhibits two conformations in DMSO solution due to cis-trans isomerism about the Gly-Pro peptide bond. Surprisingly the cis-Gly-Pro segment in the minor isomers is not involved in a beta VI-turn, but forms a turn structure with cis-Gly-Pro in the i and i + 1 positions. Although no stabilizing hydrogen bond is found in this turn, the phi- and psi-angles closely correspond to a beta I-turn [Pro2: phi(i + 1) -60 degrees, psi(i + 1) -30 degrees; Phe3: phi(i + 2) -100 degrees, psi(i + 2) -50 degrees]. Hence we call this structural element a pseudo-beta I-turn. As expected, in the dominating all-trans isomers proline occupies the i + 1 position of a standard beta I-turn. Therefore, cis-trans isomerization of the Gly1-Pro2 amide bond only induces a local conformational rearrangement, with minor structural changes in other parts of the molecule. However, the geometry of the other regions is affected by the chirality of the i + 1 amino acid for both isomers (beta I for Phe5, beta II' for D-Phe5 or D-Pro5).


Asunto(s)
Oligopéptidos/química , Prolina/química , Simulación por Computador , Cristalización , Ciclización , Enlace de Hidrógeno , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Oligopéptidos/síntesis química , Conformación Proteica , Estructura Secundaria de Proteína
11.
Biopolymers ; 38(6): 705-21, 1996 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-8652792

RESUMEN

Irregular protein secondary structures are believed to be important structural domains involved in molecular recognition processes between proteins, in interactions between peptide substrates and receptors, and in protein folding. In these respects tight turns are being studied in detail. They also represent template structures for the design of new molecules such as drugs, pesticides, or antigens. Isolated alpha-turns, not participating in alpha-helical structures, have received little attention due to the overwhelming presence of other types of tight turns in peptide and protein structures. The growing number of protein X-ray structures allowed us to undertake a systematic search into the Protein Data Bank of this uncharacterized protein secondary structure. A classification of isolated alpha-turns into different types, based on conformational similarity, is reported here. A preliminary analysis on the occurrence of some particular amino acids in certain positions of the turned structure is also presented.


Asunto(s)
Bases de Datos Factuales , Estructura Secundaria de Proteína , Secuencia de Aminoácidos , Datos de Secuencia Molecular
12.
Biopolymers ; 34(11): 1505-15, 1994 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-7827262

RESUMEN

In the present paper we describe the synthesis, purification, single crystal x-ray analysis, and solution structural characterization by nmr spectroscopy, combined with restrained molecular dynamic simulations, of the cyclic hexapeptide cyclo-(Pro-Phe-beta-Ala-Phe-Phe-beta-Ala). The peptide was synthesized by classical solution methods and the cyclization of the free hexapeptide was accomplished in good yields in diluted methylenechloride solution using N,N-dicyclohexyl-carbodiimide. The compound crystallizes in the monoclinic space group P2(1) from methanol/ethyl acetate. The molecule adopts in the solid state a conformation characterized by cis beta-Ala6-Pro1 peptide bond. The alpha-amino acid residues are at the corner positions of turned structures. The Pro1-Phe2 segment is incorporated in a pseudo type I beta-turn, while Phe4-Phe5 is in a typical type I beta-turn. Assignment of all 1H and 13C resonances was achieved by homo- and heteronuclear two-dimensional techniques in dimethylsulfoxide (DMSO) solutions. The conformational analysis was based on interproton distances derived from rotating frame nuclear Overhauser effect spectroscopy spectra and homonuclear coupling constants. Restrained molecular dynamic simulation in vacuo was also performed to built refined molecular models. The molecule is present in DMSO solution as two slowly interconverting conformers, characterized by a cis-trans isomerism around the beta-Ala6-Pro1 peptide bond. This work confirms our expectations on the low propensity of beta-alanyl residues to be positioned at the corners of turned structure.


Asunto(s)
Oligopéptidos/química , Péptidos Cíclicos/química , Secuencia de Aminoácidos , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , beta-Alanina
13.
Biopolymers ; 34(11): 1517-26, 1994 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-7827263

RESUMEN

In the present paper we describe the synthesis, purification, single crystal x-ray analysis, and nmr solution characterization, combined with restrained molecular dynamic simulations, of the cyclic hexapeptide cyclo-(L-Pro-L-Phe-beta-Ala)2. The peptide was synthesized by classical solution methods and the cyclization of the free hexapeptide was accomplished in good yields in diluted methylene chloride solution using N,N-dicyclohexyl-carbodiimide. The compound crystallizes in the monoclinic space group P2(1) from methanol-dichloromethane solution. The two identical halves of the molecule adopt in the solid state two different conformations. One beta-Ala-L-Pro peptide bond is trans, while the second is cis. The molecule is present in dimethylsulfoxide d6 solutions as a mixture of conformational families. One of these corresponds to a C2 symmetrical molecule with both beta-Ala-Pro cis peptide bonds, while the second major conformation is very similar to that observed in the solid state. All Pro-Phe segments, both in the solid state and the symmetrical and unsymmetrical solution conformations, display phi, psi angles close to that of position i + 1 and i + 2 of type II beta-turns. In addition, the segments preceded by a trans beta-Ala-Pro peptide bond are characterized by a typical i<--i + 3 hydrogen bond, which is absent in the conformer containing a cis beta-Ala-Pro peptide bond. The latter conformation corresponds to a new structural domain we define as the "pseudo type II beta-turn."


Asunto(s)
Péptidos Cíclicos/química , Secuencia de Aminoácidos , Datos de Secuencia Molecular , Estructura Secundaria de Proteína , beta-Alanina
14.
Biopolymers ; 53(2): 189-99, 2000 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-10679623

RESUMEN

A solid state analysis of the cyclic octapeptide c(-Pro(1)-Pro-Phe-Phe-Ac(6)c-Ile-D-Ala-Val(8)-) (C8-CLA), containing the Pro-Pro-Phe-Phe sequence, followed by the bulky helicogenic C(alpha,alpha)-dialkylated 1-aminocyclohexane-1-carboxylic acid (Ac(6)c) residue and a D-Ala residue in position 7, has been carried out by x-ray diffraction. The crystals, grown from a DMSO solution, are monoclinic, space group P2(1) with a = 13.458(3) A, b = 19. 404(5) A, c = 21.508(4) A, and beta = 90.83(6) degrees, with two independent cyclic molecules in the asymmetric unit, two DMSO molecules, and three water molecules. The structure has been solved using the half and bake procedure by Sheldrick, and refined to final R1 and wR2 indices of 0.0613 and 0.1534 for 9867 reflections with I > 2sigma(I). This cyclic peptide, a deletion analogue of the naturally occurring cyclic nonapeptide cyclolinopeptide A [c(Pro-Pro-Phe-Phe-Leu-Ile-Ile-Leu-Val), CLA] has been designed to study the influence of the ring size reduction on the conformational behavior of CLA and more in general to obtain structural information on asymmetric cyclic octapeptides. The compound exhibits, in the solid state, a "banana-twisted" conformation with a cis peptide bond located between the two proline residues. Five intramolecular H bonds stabilize the structure: one type VIa beta-turn, two consecutive type III/I beta-turns, one gamma-turn, and one C(16) bend. The structure has also been compared with either the solution structure previously reported by us and obtained by nmr and computational analysis, and with solid state structural data reported in the literature on cyclic octapeptides.


Asunto(s)
Péptidos Cíclicos/química , Secuencia de Aminoácidos , Cristalografía por Rayos X , Modelos Moleculares , Conformación Proteica , Soluciones
15.
J Pept Sci ; 1(5): 330-40, 1995.
Artículo en Inglés | MEDLINE | ID: mdl-9223012

RESUMEN

The cyclic octapeptide cyclo[-Pro1-Pro-Phe-Phe-Ac6c-Ile-ala-Val8-] [C8-Ac6c], containing the Pro1-Pro-Phe-Phe sequence, followed by a bulky helicogenic C alpha,alpha-dialkylated glycine residue Ac6c [1-aminocyclohexane-1-carboxylic acid), and a D-Ala residue at position 7 has been synthesized. This cyclic peptide is a deletion analogue of the naturally occurring cyclic nonapeptide cyclolinopeptide A (CLA). It has been designed with the aim of studying the role that the Ac6c and D-Ala residues play on the conformational behaviour of the whole molecule and their influence on the conformation of the Pro1-Pro-Phe-Phe sequence when compared with cyclolinopeptide A. C8-Ac6c has been investigated in chloroform and acetonitrile solutions by 2D NMR techniques. Only one set of sharp signals is observed in both solvents. This evidence strongly supports the hypothesis that only one conformational state exists in the chosen solvents. The interpretation of the experimental data points to the existence for C8-Ac6c of a very rigid structure stabilized by intramolecular hydrogen bonds. The measured NOE effects allow the calculation of internuclear distances, which have been used as restraints in molecular dynamic calculations. The proposed conformation of the molecule shows that the Pro-Pro-Phe segment retains the conformation observed in natural CLA both in solution and in the solid state and that the Ac6c residue indeed reinforces the ring rigidity not permitting the formation of any appropriate cavity in which inorganic cations could be complexed.


Asunto(s)
Péptidos Cíclicos/química , Secuencia de Aminoácidos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Péptidos Cíclicos/síntesis química , Conformación Proteica , Solventes , Termodinámica
16.
Biopolymers ; 38(6): 683-91, 1996 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-8652790

RESUMEN

In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-beta-Ala-beta-Ala). This compound crystallizes in the orthorhombic space group P2I2I2I from methanol and adopts in the solid state an unusual conformation characterized by a cis beta-Ala5-Pro1 peptide bond and by an intramolecular hydrogen bond stabilizing a C11-and a C12-ring structure. The C11 structure contains the Phe3 and the beta-Ala4 at the corner position of the turn; it is the first observation of a type II beta-turn enlargement due to the insertion of an extra methylene group of the beta-alanine residue. The rest of the molecule participates in a newly characterized C12-ring structure, which incorporates a beta-Ala residue at position i of the turn.


Asunto(s)
Péptidos Cíclicos/química , beta-Alanina/análisis , Secuencia de Aminoácidos , Datos de Secuencia Molecular , Conformación Proteica
17.
Biopolymers ; 38(6): 693-703, 1996 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-8652791

RESUMEN

In the present paper we describe the solution nmr structural analysis and restrained molecular dynamic simulation of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-beta-Ala-beta-Ala). The conformational analysis carried out in CD3CN and dimethylsulfoxide (DMSO) solutions by nmr spectroscopy was based on interproton distances derived from rotating frame nuclear Overhauser effect spectroscopy spectra and homonuclear coupling constants. A restrained molecular dynamic simulation in vacuo was also performed to build refined molecular models. The molecule is present in both solvent systems as two slowly interconverting conformers, characterized by a cis-trans isomerism around the beta-Ala5-Pro1 peptide bond. In CD3CN solution, the conformer with a ci5 peptide bond is quite similar to that observed in the solid state, while the conformer containing all trans peptide bonds is characterized by an intramolecular hydrogen bond stabilizing a C10- and a C13-ring structure. In DMSO solution, the trans isomer is partly similar to that observed in CD3CN solution while the cis isomer is different from that observed in the solid state. The effect of the solvent in stabilizing different conformations was also investigated in DMSO-CD3CN solvent mixtures.


Asunto(s)
Péptidos Cíclicos/química , beta-Alanina/análisis , Secuencia de Aminoácidos , Datos de Secuencia Molecular , Conformación Proteica , Solventes
18.
Int J Pept Protein Res ; 42(5): 459-65, 1993 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-8106198

RESUMEN

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.


Asunto(s)
Amidas/química , Oligopéptidos/química , Acilación , Secuencia de Aminoácidos , Cristalografía por Rayos X , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica
19.
Proc Natl Acad Sci U S A ; 89(15): 7218-21, 1992 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-1496014

RESUMEN

The structural characterization of a beta-cyclodextrin monosubstituted with the peptide cyclo(L-His-L-Leu) is reported. This work provides an x-ray example of a covalently bound group that folds in such a way that the terminal apolar side chain is retained in the hydrophobic interior of the cone-shaped cyclodextrin cavity. 6-Deoxy-6-cyclo(L-histidyl-L-leucyl)-beta-cyclodextrin crystallizes in the space group P1 with cell dimensions a = 14.728(8) A, b = 15.084(7) A, c = 18.182(10) A, alpha = 94.36(6) degrees, beta = 95.81(5) degrees, gamma = 116.08(9) degrees; overall isotropic agreement R = 10.6% for 5703 observed reflections (Fo greater than 3 sigma). The molecular structure consists of two independent molecules with the formula C54H86N4O36.7.25H2O. Each molecule assumes a "sleeping swan"-like overall shape with the hydrophobic leucine side chain inserted inside the cavity of the macrocycle. The two independent units give rise to a head-to-tail dimer linked by hydrogen bonds occurring between primary and secondary hydroxyl groups of the two monomers. The packing of the dimers produces cavities containing water molecules. There are infinite hydrophilic channels running in the crystal, which is similar to what is found in the structures of cyclic peptides.


Asunto(s)
Ciclodextrinas/química , Dipéptidos/química , Péptidos Cíclicos/química , beta-Ciclodextrinas , Conformación de Carbohidratos , Secuencia de Carbohidratos , Espectroscopía de Resonancia Magnética/métodos , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica , Relación Estructura-Actividad , Difracción de Rayos X
20.
Biopolymers ; 36(4): 453-60, 1995 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-7578940

RESUMEN

The solid state conformational analysis of [Tyr4] cyclolinopeptide A has been carried out by x-ray diffraction studies. The crystal structure of the monoclinic form, grown from a dioxane-water mixture [alpha = 9.849 (5) A, b = 20.752 (4) A, c = 16.728 (5) A, beta = 98.83 (3) degrees, space group P21, Z = 2], shows the presence of five intramolecular N-H...O = C hydrogen bonds, with formation of one C17 ring structure, one alpha-turn (C13), one inverse gamma-turn (C7), and two beta-turns (C10, one of type III and one of type I). The Pro1-Pro2 peptide unit is cis (omega = 5 degrees), all others are trans. The structure is almost superimposable with that of cyclolinopeptide A. The rms deviation for the atoms of the backbones is on the average 0.33 A.


Asunto(s)
Péptidos Cíclicos/química , Conformación Proteica , Secuencia de Aminoácidos , Cristalografía por Rayos X , Enlace de Hidrógeno , Modelos Moleculares , Datos de Secuencia Molecular , Pliegue de Proteína
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA