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AbstractA structural and spectroscopic study of 5-chloroorotic acid (5-ClOA) biomolecule was carried out by IR and FT-Raman and the results obtained were compared to those achieved in 5-fluoroorotic acid and 5-aminoorotic acid compounds. The structures of all possible tautomeric forms were determined using DFT and MP2 methods. To know the tautomer form present in the solid state, the crystal unit cell was optimized through dimer and tetramer forms in several tautomeric forms. The ketoform was confirmed through an accurate assignment of all the bands. For this purpose, an additional improvement in the theoretical spectra was carried out using linear scaling equations (LSE) and polynomic equations (PSE) deduced from uracil molecule. Base pairs with uracil, thymine and cytosine nucleobases were optimized and compared to the natural Watson-Crick (WC) pairs. The counterpoise (CP) corrected interaction energies of the base pairs were also calculated. Three nucleosides were optimized based on 5-ClOA as nucleobase, and their corresponding WC pairs with adenosine. These modified nucleosides were inserted in DNA:DNA and RNA:RNA microhelices, which were optimized. The position of the -COOH group in the uracil ring of these microhelices interrupts the DNA/RNA helix formation. Because of the special characteristic of these molecules they can be used as antiviral drugs.Communicated by Ramaswamy H. Sarma

AbstractBase pairs of 4-amino-3-nitrobenzonitrile (4A-3NBN) molecule with uracil, thymine and cytosine nucleobases were optimized and compared to natural Watson-Crick (WC) pairs. The slightly greater flexibility of the -NO2group of 4A-3NBN than the N3-H group of the natural nucleobases together with a noticeable higher dipole moment of its pairs can facilitate disruption of the DNA/RNA helix formation. Several new mutagenic modified nucleosides with 4A-3NBN and 3-amino-2-nitrobenzonitrile (3A-2NBN) were proposed as antiviral prodrugs and their base pairs optimized. The special characteristics of these prodrugs appear appropriated for their clinical use. The counterpoise (CP) corrected interaction energies of the base pairs were calculated and compared to the natural ones. The M06-2X DFT method was used for this purpose. The molecular structure of 4A-3NBN was analyzed in detail and the crystal unit cell was simulated by a tetramer form and eight dimer forms. The performance of the B3LYP, X3LYP and M06-2X methods was tested on the vibrational wavenumbers in the monomer, dimer and tetramer forms of 4A-3NBN. The observed IR and Raman bands were assigned according to the optimum dimer IIform determined by B3LYP and by the tetramer form calculated by M06-2X, which is the expected unit cell that forms the crystal net. The two best scaling procedures were used.Communicated by Ramaswamy H. Sarma

AbstractThis study focuses on the effects of the bromine atom on the molecular structure parameters in the main tautomeric forms of 5-bromouracil (5BrU), and as well, its effect on hydration and on the Watson-Crick (WC) pairs as compared to uracil molecule. The influence of the bromine atom was studied in several environments. The hydration effect on the molecular structure and energies of the main tautomeric forms of 5BrU was analyzed by considering a variable number of water molecules in explicit form up to 30 to simulate the first and second hydration shells. The ‘mutagenic’ 2-hydroxy-4-oxo (U2) enoltautomer of 5BrU, but not of uracil, was absolutely favored over the ketoform in clusters with more than 20 water molecules. For all calculations, B3LYP and M06-2X Methods were used. The effect of the bromine atom when it was inserted into the natural and reverse WC pairs uridine-adenosine was also determined, and counterpoise (CP) corrected interaction energies were calculated. The effect of the bromine atom was analyzed in several DNA:RNA hybrid microhelices. Different backbone and helical parameters were calculated and compared. The bromine atom destabilizes its base pair, with a remarkable increase in the riseparameter (Dz) corresponding to the microhelix, and to a slight increase in the diameter (d). Molecular docking calculations were also carried out with 5BrU for targeted proteins associated with diabetes, hepatocellular carcinoma and breast and lung cancers. The molecular docking analysis confirms that the 5BrU molecule may play an important role as a promising inhibitor against breast cancer.Communicated by Ramaswamy H. Sarma

The effect of the sulphur atom on 2-thiouracil (2TU) and 2-thiouridine molecules, as compared with uracil and uridine molecules, respectively, was carried out in several environments. The predicted IR spectrum of 2TU in the isolated state was compared with that obtained for uracil molecule and with those reported experimentally in matrix isolation. Its crystal unit cell in the solid state was simulated through a tetramer form using DFT methods for the first time. The calculated Raman spectrum was compared to the experimental ones in the solid state. A linear scaling procedure was used for this task. The first hydration shell was simulated by explicit number of water molecules surrounding 2TU up to 30 and was compared with that obtained in uracil molecule. Water molecules ‘distributed’ around 2TU was preferred over that ‘clustering’, because it can better reproduce the hydration and their effects on different parameters of the molecular structure of 2TU and uracil. The total atomic charges and several calculated thermodynamic parameters were discussed. The effect of the sulphur atom on the Watson-Crick (WC) and reverse WC base pair uridine-adenosine was estimated, and the CP corrected interaction energies were calculated. 2-thiouridine has a weaker WC pair than that with uridine, although its slight higher dipole moment (μ) facilitates the interaction with the water molecules. Several helical parameters were determined.

Endoscopic ligation is the standard therapy for secondary prophylaxis of variceal bleeding, being a simple procedure, although not without complications. A case of a rare complication is presented.

A comprehensive theoretical conformational analysis of the anti-HIV Nikavir prodrug was carried out; this prodrug has noticeable advantage over the approved drug AZT. The whole conformational parameters (χ, α, β, γ, δ, ϕ, Pand νmax) were analysed as well as the NBO natural atomic charges. The calculations were carried out by means of DFT/B3LYP and ab initioMP2 methods with full relaxation of all geometrical parameters. The search located at least 67 stable structures, 4 of which were within a 1 kcal/mol electronic energy range of the global minimum. By MP2 it corresponds to the calculated values of the exocyclic torsional angles χ = –108.0°, β = 14.5°, γ = 76.7° and ε = 71.5°. The results obtained are in accordance to those found in related anti-HIV nucleoside analogues. Comparisons of the conformers with those determined in the common anti-HIV drug AZT were carried out. A detailed analysis of the lowest vibrations (<200 cm−1) in the best conformer of Nikavir was carried out. The most stable hydrated cluster of this conformer with 20 explicit water molecules was determined.Calculations in five of its 6′-derivatives were performed to identify structural trends that might correlate with the anti-HIV activity of these compounds. Ten structure–activity relationships/tendencies were established that can help for the design of new drugs. Several recommendations for this design were expressed.

5-iodo-2′-deoxyuridine Nucleoside Analogue (IUdR) was the first selective antiviral nucleoside against herpes simplex virus type 1 and 2, and it was also a meaningful anticancer drug. Within a full study of this drug and its possible behaviour, previously, a comprehensive theoretical conformational analysis by MP2 and B3LYP was carried out, and all the possible stable structures were determined with full relaxation of all geometrical parameters. The search located 45 stable structures, and in all them, the whole conformational parameters (, , , , , P, max) were analyzed as well as the NBO natural atomic charges. Comparisons of the conformers with those of the natural Nucleoside 2′-deoxythymidine (dT) were carried out, and the main differences between IUdR and dT were analyzed. The accuracy of the methods used was probed with the simulation of the X-ray crystal data by a tetramer form. Watson-Crick (WC) IUdR/dT···2′-deoxyadenosine pairs were analyzed for the first time using quantum chemical calculations, as well as the mispairing IUdR/dT···2′-deoxyguanosine. As result, it is observed that IUdR give rises to a slightly stronger WC pair and weaker mispairing than those with dT, therefore deforming slightly the DNA axis and difficulting the growth of the DNA virus and consequently, killing it.

The structure of benzoic acid as monomer was studied by semiempirical, ab initio, and density functional methods using several basis sets. The performance of these methods in calculating and describing the vibrational frequencies of benzoic acid and several derivatives was determined. The cyclic dimer form of benzoic acid was also reproduced. Two new procedures of scaling the frequencies were presented. For the ring modes, specific scale equations and scale factors were used from benzene molecule. For the carboxylic group, scaling equations and specific scale factors at different levels were also determined to be used in benzoic acid derivatives. A reassignment of several bands was done. A comparison of the cost/effective method and procedure of scaling was carried out. A significant reduction of the error in the predicted frequencies was obtained over the one-factor standard scaling procedure. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

The structure of benzoic acid as monomer was studied by semiempirical, ab initio, and density functional methods using several basis sets. The performance of these methods in calculating and describing the vibrational frequencies of benzoic acid and several derivatives was determined. The cyclic dimer form of benzoic acid was also reproduced. Two new procedures of scaling the frequencies were presented. For the ring modes, specific scale equations and scale factors were used from benzene molecule. For the carboxylic group, scaling equations and specific scale factors at different levels were also determined to be used in benzoic acid derivatives. A reassignment of several bands was done. A comparison of the cost/effective method and procedure of scaling was carried out. A significant reduction of the error in the predicted frequencies was obtained over the one-factor standard scaling procedure. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

A complete vibrational analysis of the Fourier transform (FT) infrared (IR) and FT-Raman spectra of both molecules was carried out using quantum chemical calculations. The structure of phenothiazine (PTZ) and N-methylphenothiazine (N-MePTZ) were studied by semiempirical, and ab initio methods. Different basis sets and two new procedures for scaling the frequencies of the ring modes were used. Vibrational data of the methyl group in N-MePTZ were interpreted in terms of the different molecular conformations in the solid state. The ¹H- and ¹³C–nuclear magnetic resonance (NMR) data were interpreted in terms of the electron densities on the atoms and the stacking solute–solute association in dimethyl sulfoxide solution. Chemical shifts were related to the Merz-Kollman atomic charges. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002

FTIR and FT-Raman spectra of 5-methyluracil (thymine) were recorded in the regions 400–4000 cm⁻¹ and 50–4000 cm⁻¹, respectively. The observed wavenumbers were analysed and assigned to different normal modes of vibration of the molecule. Ab initio and density functional calculations were performed to support the assignments of the observed wavenumbers. The geometry structure was determined and a comparison with the uracil molecule was made. Good reproducibility of the experimental wavenumbers was obtained at the B3LYP level and the percentage error was very small, less than 1% in most cases. Copyright © 2000 John Wiley & Sons, Ltd.

Geometries, frequencies and energetics of tetrahedral-like (classical) and inverted forms of several silanes SiH3–XHn(X=Be, Mg, B, Al, N, P and S), where nis 1 or 2 depending on the X atom, were determined using ab initio wavefunction and DFT methods, and several basis sets including polarization and diffuse functions. Vibrational harmonic frequencies are also discussed and compared with experimental data where available. The error in the calculated frequencies is analyzed and reduced by using scaling formulas.

FT Raman study of 5-fluorouracil, an anticarcinogenic drug, was carried out. Ab initio and density functional computations of the vibrational spectrum, the molecular geometry, the atomic charges, the total energy, the zero point energy, the rotational constants, the room temperature entropy, (translational, rotational and vibrational) and dipole moment were carried out. The observed Raman wavenumbers were analysed in light of the computed vibrational spectrum. Thermodynamic functions, namely, the enthalpy, the entropy, the heat capacity and the free energy were also computed in the temperature range 200–1000 K using the rigid-rotor harmonic oscillator approximation. For this purpose the fundamental wavenumbers were taken from the present FT-Raman spectrum and the structural parameters were taken from the present theoretically computed geometry. Copyright © 2000 John Wiley & Sons, Ltd.

Objective To evaluate whether sensitivity and specificity of tachypnoea for the diagnosis of pneumonia change with age, nutritional status, or duration of disease. Methods Diagnostic testing of 110 children with acute respiratory infection, 51 of whom presented with tachypnoea. The gold standard was a chest roentgenogram. Thirty five children had a radiological image of pneumonia; 75 were diagnosed as not having pneumonia. Sensitivity, specificity, and percentage of correct classification of tachypnoea, by itself or in combination with other clinical signs for all children, by age groups, nutritional status, and disease duration were calculated. Results Tachypnoea as the sole clinical sign showed the highest sensitivity (74%) and a specificity of 67%; 69% of cases were classified correctly. Sensitivity was reduced when other clinical signs were combined with tachypnoea, and there was no significant increase in correct classification, although specificity increased to 84%. In children with a disease duration of less than three days, tachypnoea had a lower sensitivity and specificity (55% and 64%, respectively), and a lower percentage of correct classification (62%). In children with low weight for age (&lt; 1 Z-score), tachypnoea had a sensitivity of 83%, a specificity of 48%, and 60% correct classification. Sensitivity and specificity did not vary with age groups. Conclusions Tachypnoea used as the only clinical sign is useful for identifying pneumonia in children, with no significant variations for age. In children with low weight for age, tachypnoea had higher sensitivity, but lower specificity. However, during the first three days of disease, the sensitivity, specificity, and percentage of correct classification were significantly lower.

The controlled attenuation parameter (CAP) allows the indirect measurement of liver fat and the indirect the indirect measurement of liver fat and stiffness by transient elastography. Its diagnostic utility has been validated, but the factors for its reliability are unknown. Therefore, the objective is to evaluate the predictors of CAP quality by transient elastography.

Several theoretical methods were used to obtain the relationships between the geometric parameters of the amino group in para-substituted anilines. Several equations were established. These relations were found in the majority of the cases as linear or slightly parabolic with a correlation coefficient close to the value one. The study was extended to the stretching frequencies of the amino group. Some general conclusions were drawn.

The gaseous general anesthetic halothane (CF3–CHBrCl) was studied by ab initio and density functional methods. The calculated vibrational spectrum was compared with the experimental ones. Scaling coefficients were used in the frequencies to improve the theoretical spectra, with errors lower than 0.5%. The infrared and Raman spectra were predicted.

The performance of semiempirical, ab initio, and density functional methods in calculating and describing the vibrational frequencies of benzene and several derivatives was determined. Different levels were used. The normal modes of the ring were characterized by the magnitude and direction of the displacement vector. Two new procedures of scaling the frequencies were presented. Scaling factors were determined at different levels. A significant reduction in the predicted frequencies of the ring modes of several benzene derivatives was obtained over the one-factor overall scaling procedure.

Geometry, energetics, and dipole moments of tetrahedral-like (classical) and inverted forms of SiXnH3-nLi and SiXnH3-nNa, where X stands for a halogen atom, are studied ab initio at HF, MP2, QCISD(T), and B3LYP levels of the theory using triple-ζ plus polarization and diffuse functions basis sets. The inverted form is found to be the most stable for all the cases where Li is present but not in all the cases involving Na. Energy differences between classical and inverted forms range from −2 to 24 kcal mol^-1. The results for SiH3Li agree with previous data. Agreement of the properties determined using this methodology with the experimental results, where available, is found very satisfactory. An analysis of the bonding in these molecules in terms of atomic charges and electron density is carried out.

In Tlaxcala, Mexico, 80% of the children who died from diarrhoea or acute respiratory infections (ARI) in 1992-1993 received medical care; in more than 70% of cases it was provided by a private general practitioner (GP). The present study evaluated the quality of case management by private and public GPs to children under five years of age with diarrhoea and ARI. During the clinical observation, the treatment and counselling given to the mother were assessed with the WHO guidelines as reference standard. A total of 41 private and 40 public GPs were evaluated for the management of diarrhoea, and 59 private and 40 public GPs for the management of ARI. For diarrhoea, half of the private GPs gave inadequate rehydration therapy, 63% gave incorrect advice on diet, 66% and 49% made an incorrect decision in the prescription of antimicrobial and symptomatic drugs, respectively. Public GPs generally performed better in diarrhoea management: 7% gave inadequate rehydration therapy, 13% gave wrong advice on diet, 3% made a wrong decision in the prescription of symptomatic drugs and 28% gave a wrong decision in antimicrobial prescription. In the management of ARI, 66% and 58% of private GPs made a wrong decision in the prescription of antimicrobial and symptomatic drugs, respectively, compared to 30% and 20% of public GPs, respectively. Counselling to the mother given by both private and public GPs was considered inadequate in most cases of diarrhoea and ARI. These results clearly show that private doctors, as important providers of medical care, need to be included in the strategies to improve the quality of care of children with diarrhoea and ARI. Future research needs to address the determinants of the clinical practice of private doctors in countries like Mexico.

The vibrational spectra of p-methoxybenzoic acid (anisic acid) were calculated and compared with the experimental spectra. All measured bands in the IR and Raman spectra were interpreted in terms of calculated vibrations from the AM1 and 4–21G* methods, and their frequencies were correlated. Several scale coefficients were used to improve the theoretical spectra. The optimum geometric parameters were also computed with the AM1 semiempirical method and with the 4–21G* ab initioprocedure.

In the two stable conformations of the diazabicyclanol 3, 7-dimethyl-3, 7-diazabicyclo[3. 3. 1]nonan-9-ol, chair-chair (Va) and chair-boat (Vb), the infrared spectra (200-4000 cm-1) were recorded, compared and their vibrations analysed. Using the AMI senlempirical method, the geometry was fully optimized in both forms, and the theoretical Infrared spectra were calculated and compared. In the (Vb) conformation, the IR spectra were recorded in CCl3D, CCl4 and S2C solvents. Some correlations were established.

The infrared and Laser Raman spectra of procaine with free basis in the solid state were obtained. The characteristic vibrational frequencies of their different modes were identified and assigned from isotope shifts and theoretical calculations. An infrared study in the liquid phase was also carried out. The corresponding rotation and inversion barriers in p-amino group were computed by means of different optimization procedures.

The infrared and laser Raman spectra (100-4000 cm1) of benzocaine hydrochloride were recorded and its vibrations analysed. A theoretical spectrum with the AM1 semiempirical method was calculated. An infrared study with the temperature was also made. From the experimental data, the torsion and inversion barriers of amine group were calculated.

In Tlaxcala, Mexico, 80% of the children who died from diarrhoea or acute respiratory infections (ARI) in 1992-1993 received medical care; in more than 70% of cases it was provided by a private general practitioner (GP). The present study evaluated the quality of case management by private and public GPs to children under five years of age with diarrhoea and ARI. During the clinical observation, the treatment and counselling given to the mother were assessed with the WHO guidelines as reference standard. A total of 41 private and 40 public GPs were evaluated for the management of diarrhoea, and 59 private and 40 public GPs for the management of ARI. For diarrhoea, half of the private GPs gave inadequate rehydration therapy, 63% gave incorrect advice on diet, 66% and 49% made an incorrect correct decision in the prescription of antimicrobial and symptomatic drugs, respectively. Public GPs generally performed better in diarrhoea management: 7% gave inadequate rehydration therapy, 13% gave wrong advice on diet, 3% made a wrong decision in the prescription of symptomatic drugs and 28% gave a wrong decision in antimicrobial prescription. In the management of ARI, 66% and 58% of private GPs made a wrong decision in the prescription of antimicrobial and symptomatic drugs, respectively, compared to 30% and 20% of public GPs, respectively. Counselling to the mother given by both private and public GPs was considered inadequate in most cases of diarrhoea and ARI. These results clearly show that private doctors, as important providers of medical care, need to be included in the strategies to improve the quality of care of children with diarrhoea and ARI. Future research needs to address the determinants of the clinical practice of private doctors in countries like Mexico.

AbstractThe low spectral region of procaine was studied by far-infrared spectroscopy. Raman lines were registered and interpreted. An equivalent study was performed on the molecule of benzocaine. In the characterization of the bands, and in the description of the torsion-inversion mode of the p-amino group, the AM1 semiempirical method was used. The optimum geometry parameters, the torsion and inversion potential functions, the energy levels, and the transitions were obtained. The effects of temperature on the torsion and inversion modes were studied.

Two conformations of minimum energy (I-syn and I-anti) were found in meta-aminobenzoic acid by the AMI semiempirical method. All the geometric parameters were optimized and compared with published data obtained by means of X-ray diffraction. The dipolar form of meta-aminobenzoic acid was also optimized by AM1. The vibrational spectra were computed in all cases. Several scale coefficients were used to improve the theoretical spectra. The total atomic charges, the electronic density and several thermodynamics parameters were also calculated.

We have carried out quantum chemical calculations for a series of N-nitramines (H2NNO2, MeNHNO2, CINHNO2, MeNClNO2, Me2NNO2) using the GAUSSIAN-90 program by the restricted Hartree—Fock method, taking into account electron correlation according to Møller—Plesset second-order perturbation theory in a standard 6–31G* basis. In this paper, we present the geometric parameters of the equilibrium forms of the molecules obtained as a result of full optimization. The calculation allowed us to establish that with an increase in electronegativity of the substituents on the amine nitrogen atom, we observe coordinated lengthening of the NN bond, shortening of the N=O bond, and increase in the pyramidal character of the configuration of the bonds of the amine nitrogen atoms. We observed a close to linear relationship between the length of the NN bond and the magnitude of the angle of deviation of this bond from the plane of the ONO atoms. The greatest difference in NN bond lengths (0.06 Å) occurs between the Me2NNO2 and ClNHNO2 molecules.

AbstractThe vibrational frequencies of several silanes H3SiX (X=BH2, AlH2, PH2and SH) are determined. The infrared and Raman spectra are plotted. Several scale procedures were use to improve the theoretical spectra. The geometric parameters in the planar, staggeredand eclipsedstructures of these species are fully optimized and compared with ab initio calculations. Basis set effects on the calculated structures are discussed. A few thermodynamic parameters, net atomic charges, dipole moment and energy are also computed.

The vibrational spectra of diphenylacetylene and its deuterated forms were recorded, compared and their vibrations analysed. Using the AMI semiempirical method, the optimum geometric parameters of diphenylacetylene (tolane) and four halo-substituted were obtained, and the theoretical infrared spectra were calculated and compared. Several vibrational modes, especially in the low frequency range, were established. A few thermodynamic parameters, net atomic charges and atomic electron density were computed.

For Abstract see ChemInform Abstract in Full Text.