Characterization of currently marketed heparin products: analysis of molecular weight and heparinase-I digest patterns

We evaluated polyacrylamide gel electrophoresis (PAGE) and size exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS) approaches to determine weight-average molecular weight (M _w) and polydispersity (PD) of heparins. A set of unfractionated heparin sodium (UFH) and low-molecular-weight heparin (LMWH) samples obtained from nine manufacturers which supply the US market were assessed. For SEC-MALLS, we measured values for water content, refractive index increment (dn/dc), and the second virial coefficient (A ₂) for each sample prior to molecular weight assessment. For UFH, a mean ± standard deviation value for M _w of 16,773 ± 797 was observed with a range of 15,620 to 18,363 (n = 20, run in triplicate). For LMWHs by SEC-MALLS, we measured mean M _w values for dalteparin, tinzaparin, and enoxaparin of 6,717 ± 71 (n = 4), 6,670 ± 417 (n = 3), and 3,959 ± 145 (n = 3), respectively. PAGE analysis of the same UFH, dalteparin, tinzaparin, and enoxaparin samples showed values of 16,135 ± 643 (n = 20), 5,845 ± 45 (n = 4), 6,049 ± 95 (n = 3), and 4,772 ± 69 (n = 3), respectively. These orthogonal measurements are the first M _w results obtained with a large heparin sample set on product being marketed after the heparin crisis of 2008 changed the level of scrutiny of this drug class. In this study, we compare our new data set to samples analyzed over 10 years earlier. In addition, we found that the PAGE analysis of heparinase digested UFH and neat LMWH samples yield characteristic patterns that provide a facile approach for identification and assessment of drug quality and uniformity.     

Broad-spectrum drug screening of meconium by liquid chromatography with tandem mass spectrometry and time-of-flight mass spectrometry

Analysis of the major drugs of abuse in meconium has been established in clinical practice for detecting fetal exposure to illicit drugs, particularly for the ready availability of the sample and ease of collection from diapers, compared with neonatal hair and urine. Very little is known about the occurrence and detection possibilities of therapeutic and licit drugs in meconium. Meconium specimens (n = 209) were collected in delivery hospitals, from infants of mothers who were suspected to be drug abusers. A targeted analysis method by liquid chromatography–triple quadrupole mass spectrometry (LC-MS/MS) was developed for abused drugs: amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, morphine, codeine, 6-monoacetylmorphine, oxycodone, methadone, tramadol, buprenorphine, and norbuprenorphine. A separate LC-MS/MS method was developed for 11-nor-∆⁹-tetrahydrocannabinol-9-carboxylic acid. A screening method based on LC coupled to time-of-flight MS was applied to a broad spectrum of drugs. As a result, a total of 77 different compounds were found. The main drug findings in meconium were as follows: local anesthetics 82.5% (n = 172), nicotine or its metabolites 61.5% (n = 129), opioids 48.5% (n = 101), stimulants 21.0% (n = 44), hypnotics and sedatives 19.0% (n = 40), antidepressants 18.0% (n = 38), antipsychotics 5.5% (n = 11), and cannabis 3.0% (n = 5). By revealing drugs and metabolites beyond the ordinary scope, the present procedure helps the pediatrician in cases where maternal denial is strong but the infant seems to suffer from typical drug-withdrawal symptoms. Intrapartum drug administration cannot be differentiated from gestational drug use by meconium analysis, which affects the interpretation of oxycodone, tramadol, fentanyl, pethidine, and ephedrine findings.     

Identification of free and conjugated metabolites of mesocarb in human urine by LC-MS/MS

The objective of the present study was to investigate mesocarb metabolism in humans. Samples obtained after administration of mesocarb to healthy volunteers were studied. The samples were extracted at alkaline pH using ethyl acetate and salting-out effect to recover metabolites excreted free and conjugated with sulfate. A complementary procedure was applied to recover conjugates with glucuronic acid or with sulfate consisting of the extraction of the urines with XAD-2 columns previously conditioned with methanol and deionized water; the columns were then washed with water and finally eluted with methanol. In both cases, the dried extracts were reconstituted and analyzed by ultra-performance liquid chromatography–tandem mass spectrometry. Chromatographic separation was carried out using a C₁₈ column (100 mm × 2.1 mm i.d., 1.7 μm particle size) and a mobile phase consisting of water and acetonitrile with 0.01% formic acid with gradient elution. The chromatographic system was coupled to a mass spectrometer with an electrospray ionization source working in positive mode. Metabolic experiments were performed in multiple-reaction monitoring mode by monitoring one transition for each potential mesocarb metabolite. Mesocarb and 19 metabolites were identified in human urine, including mono-, di-, and trihydroxylated metabolites excreted free as well as conjugated with sulfate or glucuronic acid. All metabolites were detected up to 48 h after administration. The structures of most metabolites were proposed based on data from reference standards available and molecular mass and product ion mass spectra of the peaks detected. The direct detection of mesocarb metabolites conjugated with sulfate and glucuronic acid without previous hydrolysis has been described for the first time. Finally, a screening method to detect the administration of mesocarb in routine antidoping control analyses was proposed and validated based on the detection of the main mesocarb metabolites in human urine (p-hydroxymesocarb and p-hydroxymesocarb sulfate). After analysis of several blank urines, the method demonstrated to be specific. Extraction recoveries of 100.3 ± 0.8 and 105.9 ± 10.8 (n = 4), and limits of detection of 0.5 and 0.1 ng mL⁻¹ were obtained for p-hydroxymesocarb sulfate and p-hydroxymesocarb, respectively. The intra- and inter-assay precisions were estimated at two concentration levels, 50 and 250 ng mL⁻¹, and relative standard deviations were lower than 15% in all cases (n = 4).     

MALDI-TOF/TOF CID study of poly(α-methylstyrene) fragmentation reactions

MALDI-TOF/TOF CID experiments are reported for hydroxylated poly(α-methylstyrene) precursor ions (PAMS: m/z 1,445.9 (n = 10), 2,036.3 (n = 15), 2,626.7 (n = 20), 3,217.1 (n = 25), and 3,807.5 (n = 30), where the number of repeat units n corresponds to the oligomer mass numbers). The influences of structure, molecular weight, and kinetic energy on degradation mechanisms were examined to test the generality of our multi-chain fragmentation model developed for polystyrene. Our results indicate that poly(α-methylstyrene) free radicals are formed initially through multiple chain breaks and subsequently undergo a variety of depolymerization reactions to yield predominantly monomer and dimer species; the intensity of each species depends on the effective kinetic energy selected for the CID process. Each depolymerization mechanism is presented in detail with experimental and computational data to justify/rationalize the process and its kinetic energy dependence. These processes show the complex interrelationships between the various pathways along with preferred production of tertiary radicals, which suppresses the appearance of primary radicals. Additionally, Py-GC/MS experimental data are presented to allow a comparison of the multimolecular free radical reactions in pyrolysis with the unimolecular fragmentation reactions of MS/MS. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Cage Structure Formation of Singly Doped Aluminum Cluster Cations Al<Subscript><Emphasis Type="BoldItalic">n</Emphasis></Subscript><Emphasis Type="BoldItalic">TM</Emphasis><Superscript>+</Superscript> (<Emphasis Type="BoldItalic">TM</Emphasis> = Ti,V, Cr)

Structural information on free transition metal doped aluminum clusters, Al _n TM ⁺ (TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size (n = 5 – 35) and temperature (T = 145 – 300 K) dependent investigations reveal that bare Al _n ⁺ clusters are inert toward argon, while Al _n TM ⁺ clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum cage. The critical size, n _crit , is found to be surprisingly large, namely n _crit = 16 and n _crit = 19 – 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster–argon bond dissociation energies have been derived as function of cluster size from equilibrium mass spectra and are in the 0.1–0.3 eV range.     

Development of a highly precise ID-ICP-SFMS method for analysis of low concentrations of lead in rice flour reference materials

Microwave digestion and isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-SFMS) has been applied to the determination of Pb in rice flour. In order to achieve highly precise determination of low concentrations of Pb, the digestion blank for Pb was reduced to 0.21 ng g⁻¹ after optimization of the digestion conditions, in which 20 mL analysis solution was obtained after digestion of 0.5 g rice flour. The observed value of Pb in a non-fat milk powder certified reference material (CRM), NIST SRM 1549, was 16.8 ± 0.8 ng g⁻¹ (mean ± expanded uncertainty, k = 2; n = 5), which agreed with the certified value of 19 ± 3 ng g⁻¹ and indicated the effectiveness of the method. Analytical results for Pb in three brown rice flour CRMs, NIST SRM 1568a, NIES CRM 10-a, and NIES CRM 10-b, were 7.32 ± 0.24 ng g⁻¹ (n = 5), 1010 ± 10 ng g⁻¹ (n = 5), and 1250 ± 20 ng g⁻¹ (n = 5), respectively. The concentration of Pb in a candidate white rice flour reference material (RM) sample prepared by the National Metrology Institute of Japan (NMIJ) was observed to be 4.36 ± 0.28 ng g⁻¹ (n = 10 bottles). Figure Digestion blank of Pb was carefully reduced to approximately 0.2 ng g^-1 which permitted the highly precise determination of Pb at low ng g^-1 level in foodstuff samples by ID-SFMS     

Metabolic footprinting of tumorigenic and nontumorigenic uroepithelial cells using two-dimensional gas chromatography time-of-flight mass spectrometry

In this study, gas chromatography mass spectrometry (GC-MS) and two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) were employed for the metabolic footprinting of a pair of immortalized human uroepithelial cells namely HUC-1 (nontumorigenic) and HUC T-2 (tumorigenic). Both HUC-1 and HUC T-2 cell lines were cultivated in 1 mL of Ham’s F-12 media. Subsequent to 48 h of incubation, 200 μL of cell culture supernatant was protein-precipitated using 1.7 mL of methanol and an aliquot of 1.5 mL of the mixture was separated, dried, trimethylsilyl-derivatized, and analyzed using GC-MS and GC×GC-TOFMS. Metabolic profiles were analyzed using multivariate data analysis techniques to evaluate the changes of the metabolomes. Both GC-MS and GC×GC-TOFMS analyses showed distinct differences in metabolic phenotypes of the normal and tumorigenic human bladder cells (partial least squares-discriminant analysis (PLS-DA) of GC×GC-TOFMS data; two latent variables, R ² X = 0.418, R ² Y = 0.977 and Q ² (cumulative) = 0.852). Twenty metabolites were identified as being statistically different between the two cell types. These metabolites revealed that several key metabolic pathways were perturbed in tumorigenic urothelial cells as compared to the normal cells. Application of GC×GC-TOFMS offered several advantages compared to classical one-dimensional GC-MS which include enhanced chromatographic resolution (without increase in analytical run time), increase in sensitivity, improved identification of metabolites, and also separation of reagent artifacts from the metabolite peaks. Our results reinforced the advantages of GC×GC-TOFMS and the role of metabolomics in characterizing bladder cancer biology using in vitro cell culture models.     

1H NMR-based metabolomics approach for exploring urinary metabolome modifications after acute and chronic physical exercise

Metabolomics is a comprehensive method for metabolite assessment that involves measuring the overall metabolic signature of biological samples. We used this approach to investigate biochemical changes due to acute and chronic physical exercise. Twenty-two women using identical oral contraceptives were segregated into an untrained (n = 10) or trained (n = 12) group depending on their physical training background. The subjects performed two exercises in a randomized order: a prolonged exercise test (75% of their \mathop V^· \textO_2   max \mathop V\limits^\cdot {{\text{O}}_{2\,\;\max }} until exhaustion) and a short-term, intensive exercise test (short-term, intensive exercise anaerobic test). Urine specimens were collected before and 30 min after each test. The samples were analyzed by ¹H NMR spectroscopy, and multivariate statistical techniques were utilized to process the data. Distinguishing characteristics were observed only in the urine profiles of specimens collected before vs. 30 min after the short-term, intensive exercise test. The metabolites responsible for such changes were creatinine, lactate, pyruvate, alanine, β-hydroxybutyrate, acetate, and hypoxanthine. In both groups, the excretion of lactate, pyruvate, alanine, β-hydroxybutyrate, and hypoxanthine increased similarly after the completion of the short-term, intensive exercise test (p < 0.03). However, acetate excretion increased to a lesser extent in trained than in untrained subjects (p < 0.05). In conclusion, metabolomics is a promising tool in order to gain insight into physiological status and to clarify the changes induced by short-term, intense physical exercise.     

Synthesis and characterization of poly(styrene/α-t-butoxy-ω-vinylbenzyl-polyglycidol) microspheres

Polystyrene microspheres with polyglycidol (polyGL) in a surface layer were synthesized in batch radical emulsifier-free emulsion copolymerizations of styrene and surfmers, α-t-butoxy-ω-vinylbenzyl-polyGL macromonomers (VB-polyGL). Macromonomers with number-average molecular weight Mˉ _n=950 (VB-polyGL950) and Mˉ _n=2700 (VB-polyGL2700) were used for these polymerizations. In all syntheses the initial concentrations of styrene and initiator (K₂S₂O₈) were constant. The initial macromonomer-to-styrene ratios were varied from 1.10 × 10⁻³ to 1.64 × 10⁻² mol/mol and from 3.46 × 10⁻⁴ to 3.47 × 10⁻³ mol/mol for VB-polyGL950 and VB-polyGL2700, respectively. The diameters of microspheres obtained were smaller for the syntheses with higher concentrations of macromonomers. Syntheses with VB-polyGL950 yielded microspheres with number-average diameters (Dˉ _n) from 216 to 900 nm and with a bimodal diameter distribution. The number-average diameters of microspheres obtained with VB-polyGL2700 varied from 220 to 650 nm, depending on the initial concentration of macromonomer. Their diameter distributions were monomodal, with a diameter polydispersity parameter (ratio of weight-average and number-average diameters) in the range 1.007≤Dˉ _w/Dˉ _n≤1.022. For each type of microsphere the fraction of polyGL in a surface layer and the surface concentration of sulfate anions were determined. The fraction of polyGL in the surface layer was related to the initial monomer composition in the polymerizing mixture. Adsorption of human serum albumin onto surfaces of some poly(styrene/VB-polyGL) microspheres was up to 10 times lower than for the polystyrene microspheres obtained in a similar emulsifier-free emulsion polymerization of styrene. Received: 26 September 2000/Accepted: 19 February 2001     

Polymer diffusion in high-M/low-M hard-soft latex blends

This paper describes experiments that investigate the use of low glass transition temperature (T _g) latex particles consisting of oligomer to promote polymer diffusion in films formed from high molar mass polymer latex. The chemical composition of both polymers was similar. Fluorescence resonance energy transfer (FRET) was used to follow the rate of polymer diffusion for samples in which the high molar mass polymer was labeled with appropriate donor and acceptor dyes. In these latex blends, the presence of the oligomer (with M _n = 24,000 g/mol, M _w/M _n = 2) was so effective at promoting the interdiffusion of the higher molar mass poly(butyl acrylate-co-methyl methacrylate; PBA/MMA = 1:1 by weight) polymer (with M _n = 43,00 g/mol, M _w/M _n = 3) that a significant amount of interdiffusion occurred during film drying. Additional polymer diffusion occurred during film aging and annealing, and this effect could be described quantitatively in terms of free-volume theory. This paper is dedicated to Professor Haruma Kawaguchi to honor his many contributions to the field of latex particles and their applications.     

Analysis of photocurrent spectra at polybithienyl film coated on Pt

Photoelectrochemical measurements have been performed at a polybithienyl (PBT) film (doping level of 1 × 10¹⁸/cm³) deposited on a platinum electrode. The cathodic photocurrents and negative slope of the Mott-Schottky plot indicate that the PBT film has the features of a p-type semiconductor. The cathodic photocurrents are interpreted in terms of the Gaertner-Butler model on the basis of the theory of the semiconductor|solution interface. The (i _ph hν)^2/n vs. hν plots taken from the photocurrent spectra show two linearities for n=1 in the wavelength range from 460 nm to 490 nm and for n=4 in the wavelength range λ > 490 nm. The band gaps of the PBT film were determined to be 2.05 ± 0.05 eV for n=1 and 1.55 ± 0.05 eV for n=4. The flat-band potential is 0.33 V (vs SCE). From the slope of the Mott-Schottky plot at the modulation frequency of 3 kHz, the dielectric constant ɛ of the film and the thickness of the depletion layer W ₀ of the PBT film were determined to be 7.4 and 0.29 μm, respectively. Received: 6 January 1999 / Accepted: 6 June 1999     

Association behavior of one-end hydrophobically modified poly[<Emphasis Type="Italic">N</Emphasis><Superscript>5</Superscript>-(2-hydroxyethyl) <Emphasis Type="SmallCaps">l</Emphasis>-glutamine] in water/ethylene glycol mixed solvent

Amphiphilic polymers Cn-PHEG consisting of water-soluble poly[N ⁵-2-(hydroxyethyl) l-glutamine] (PHEG) and hydrophobic alkyl chain (carbon number n = 12, 14, 16, or 18) attached at the PHEG terminal was prepared, and association behavior and structure of associate for Cn-PHEG in selective solvent (water/ethylene glycol mixed solvent) have been investigated. α-Helix content of PHEG block for all the polymers increased with weight fraction of ethylene glycol in the mixed solvent (W _EG). By light scattering measurements, formation of a small micelle was suggested for C14-, C16-, and C18-PHEG when W _EG = 0. With the increase in W _EG, appearance of a larger associate was revealed for C16- and C18-PHEG. Evaluated molecular weight and radius of gyration suggested that the micelle is star-like sphere when W _EG = 0 and worm-like cylinder when W _EG = 0.7. C12-PHEG did not demonstrate any distinct micellization behavior because of the weak hydrophobicity of C12 chain.     

Thermochemistry of Microhydration of Sodiated and Potassiated Monosaccharides

The thermochemical properties ΔH ^o _n , ΔS ^o _n , and ΔG ^o _n for the hydration of sodiated and potassiated monosaccharides (Ara = arabinose, Xyl = xylose, Rib = ribose, Glc = glucose, and Gal = galactose) have been experimentally studied in the gas phase at 10 mbar by equilibria measurements using an electrospray high-pressure mass spectrometer equipped with a pulsed ion beam reaction chamber. The hydration enthalpies for sodiated complexes were found to be between −46.4 and −57.7 kJ/mol for the first, and −42.7 and −52.3 kJ/mol for the second water molecule. For potassiated complexes, the water binding enthalpies were similar for all studied systems and varied between −48.5 and −52.7 kJ/mol. The thermochemical values for each system correspond to a mixture of the α and β anomeric forms of monosaccharide structures involved in their cationized complexes.     

Enantioselective piezoelectric quartz crystal sensor for d-methamphetamine based on a molecularly imprinted polymer

A piezoelectric quartz crystal (PQC) sensor based on a molecularly imprinted polymer (MIP) has been developed for enantioselective and quantitative analysis of d-(+)-methamphetamine (d(+)-MA). The sensor was produced by bulk polymerization and the resulting MIP was then coated on the gold electrode of an AT-cut quartz crystal. Conditions such as volume of polymer coating, curing time, type of PQC, baseline solvent, pH, and buffer type were found to affect the sensor response and were therefore optimized. The PQC-MIP gave a stable response to different concentrations of d(+)-MA standard solutions (response time = 10 to 100 s) with good repeatability (RSD = 0.03 to 3.09%; n = 3), good reproducibility (RSD = 3.55%; n = 5), and good reversibility (RSD = 0.36%; n = 3). The linear range of the sensor covered five orders of magnitude of analyte concentration, ranging from 10⁻⁵ to 10⁻¹ μg mL⁻¹, and the limit of detection was calculated as 11.9 pg d(+)-MA mL⁻¹ . The sensor had a highly enantioselective response to d(+)-MA compared with its response to l(−)-MA, racemic MA, and phentermine. The developed sensor was validated by applying it to human urine samples from drug-free individuals spiked with standard d(+)-MA and from a confirmed MA user. Use of the standard addition method (SAM) and samples spiked with d(+)-MA at levels ranging from 1 × 10⁻³ to 1 × 10⁻² μg mL⁻¹ showed recovery was good (95.3 to 110.9%).     

NADH screen-printed electrodes modified with zirconium phosphate,Meldola blue,and Reinecke salt. Application to the detection of glycerol by FIA

Bulk screen-printed electrodes (bSPEs) modified with zirconium phosphate (ZrP) and Meldola blue (MB) and by electrochemical deposition of a Reineckate film (bMBZrPRs-SPEs) have been constructed and used as NADH sensors. Cyclic voltammetric investigation of these bulk electrochemically modified screen-printed electrodes revealed stable catalytic activity in oxidation of the reduced form of the coenzyme nicotinamide adenine dinucleotide (NADH). Flow-injection analysis (FIA) coupled with amperometric detection confirmed the improved stability of the bMBZrPRs-SPEs (10⁻⁴ mol L⁻¹ NADH, %RSD = 4.2, n = 90, pH 7.0). Other conditions, for example applied working potential (+50 mV relative to Ag|AgCl), flow rate (0.30 mL min⁻¹) and pH-dependence (range 4.0–10.0) were evaluated and optimized. A glycerol biosensor, prepared by immobilizing glycerol dehydrogenase (GDH) on the working electrode area of a bMBZrPRs-SPE, was also assembled. The biosensor was most stable at pH 8.5 (%RSD = 5.6, n = 70, 0.25 mmol L⁻¹ glycerol). The detection and quantification limits were 2.8 × 10⁻⁶ and 9.4 × 10⁻⁶ mol L⁻¹, respectively, and the linear working range was between 1.0 × 10⁻⁵ and 1.0 × 10⁻⁴ mol L⁻¹. To assess the effect of interferences, and recovery by the probe we analyzed samples taken during fermentation of chemically defined grape juice medium and compared the results with those obtained by HPLC.     

A compact miniaturized continuous flow system for the determination of urea content in milk

A multicommutation-based flow system with photometric detection was developed, employing an analytical microsystem constructed with low temperature co-fired ceramics (LTCC) technology, a solid-phase reactor containing particles of Canavalia ensiformis DC (urease source) immobilized with glutaraldehyde, and a mini-photometer coupled directly to the microsystem which monolithically integrates a continuous flow cell. The determination of urea in milk was based on the hydrolysis of urea in the solid-phase reactor and the ammonium ions produced were monitored using the Berthelot reaction. The analytical curve was linear in the urea concentration range from 1.0 × 10⁻⁴ to 5.0 × 10⁻³ mol L⁻¹ with a limit of detection of 8.0 × 10⁻⁶ mol L⁻¹. The relative standard deviation (RSD) for a 2.0 × 10⁻³ mol L⁻¹ urea solution was lower than 0.4% (n = 10) and the sample throughput was 13 h⁻¹. To check the reproducibility of the flow system, calibration curves were obtained with freshly prepared solutions on different days and the RSD obtained was 4.7% (n = 6). Accuracy was assessed by comparing the results of the proposed method with those from the official procedure and the data are in close agreement, at a 95% confidence level.     

Quantitative in silico analysis of the selectivity of graphitic carbon synthesized by different methods

Molecular interaction energy (MI) values calculated by molecular mechanics (MM2) using a model graphitic carbon phase were used for studying the selectivity of different types of graphitic carbon columns. The MI values well correlated with logk values measured on a graphitic carbon synthesized from 100% organic materials (r = 0.961, n = 13) but not with logk values measured on a graphitic carbon synthesized using silica matrix (r = 0.558, n = 17). The latter logk values correlated well with the hydrogen bonding energy values calculated using a model silica phase (r = 0.856, n = 17). The reason for the poor correlation of the logk values measured on the latter graphitic carbon is that the silica matrix might not be completely eliminated in the production process.     

The preparation, molecular structure, and theoretical study of carbohydrazide (CHZ)

Carbohydrazide is prepared by reacting dimethyl carbonate with hydrazine hydrate. Its single crystal has been cultured with slow evaporation method. Its molecular structure and crystal structure have been determined by X-ray single crystal diffraction technique. The obtained results shows that the crystal belongs to Crystal system of Monoclinic, space group P2(1)/n with crystal parameters of a = 3.725(1), b = 8.834(2), c = 11.96(3), β = 91.97(1)°, V = 392.23(2) ³, Z = 4, D _c = 1.522 g/cm³, μ = 0.128 mm⁻¹, F0 0 0) = 192. Based on the crystal data, we have also carried quantum chemistry calculations on the title compound using the B3LYP and MP2 method with cc-pVTZ basis set. The calculation results further demonstrate the molecular structure of title compound and its coordination properties.     

Structure and stability of hypervalent NLi n Na2 (n = 1–4) and related species at density functional theory level

A number of configurations of NLi _n Na₂ (n = 1–4) species were optimized using the B3LYP–density functional theory method; the 6-31G^* basis set was used in this calculation. In order to study all possible dissociation energies, some related species such as NLi₂Na, NLi _n (n = 1–4), Li _n (n = 1, 2) and Na _n (n = 1, 2) were also considered. Optimizations of these species were followed by fundamental frequency calculations at the same level. Global minima of these species were shown to adopt C _{2 v} (NLi₄Na₂, NLi₂Na₂), D _{3 h} (NLi₃Na₂) and C _s (NLiNa₂ and NLi₂Na) configurations. All possible dissociation energies were obtained. Received: 30 November 1998 / Accepted: 15 October 1999 / Published online: 14 March 2000     

Formulas and numerical table for the radial part of overlap integrals with the same screening parameters of Slater-type orbitals

 The numerical properties of the radial part of overlap integrals with the same screening parameters in the form of polynomials in p = ξR over Slater-type orbitals have been studied and obtained by using three different methods. For that purpose, the characteristics of auxiliary functions were used first, then Fourier transform convolution theorem, and recurrence relations for the basic coefficients of A ^s _{n l λ, n ′ l ′λ} were used. The calculations of the radial part of overlap integrals with the same screening parameters were made in the range 1 ≤ n ≤ 75, 1 ≤ n′ ≤ 75, and 10⁻⁶ ≤ p. Received: 18 January 2001 / Accepted: 5 April 2001 / Published online: 27 June 2001