Facile synthesis of alpha,alpha-diisobutylglycine and anchoring its derivatives onto PAL-PEG-PS resin

alpha,alpha-Diisobutylglycine has been synthesized using a Pd-mediated dialkylation of ethyl nitroacetate as a key first step. The free alphaalphaAA is N(alpha)-protected and has been applied to the assembly of conformationally constrained peptide analogues. Mixed anhydrides from BOP-Cl and Fmoc-alphaalphaAA-OH are used for anchoring alphaalphaAAs onto a trialkoxybenzyl linker on PEG-PS grafted support, upon which a beta-strand mimic with difficult sequence is assembled in a superior quality.     

Factors affecting the quality of plutonium deposits by electrodeposition

Ultra-high resolution alpha spectrometry by microcalorimetry has demonstrated a dramatic improvement in alpha energy resolution over silicon based detectors. To characterize the optimal resolution obtained by the microcalorimeter alpha spectrometers, high quality deposits that are virtually massless are required; electrodeposition is the preferred method for the preparation of high quality deposits. In order to better understand the factors that contribute to lower alpha energy resolution and deposit yield, we have conducted a study to determine the effect of some of the parameters that are used for preparing electrodeposits. We have compared four different electrodeposition methods and four different substrate materials to determine the effect on the deposit yield and alpha energy resolution of plutonium as measured by full width at half maximum using silicon based detectors. Furthermore, we wanted to understand the effect of contaminants from environmental samples on electrodeposits. Therefore, the effect on deposit yield and alpha energy resolution with several common soil constituents (Al³⁺, Eu³⁺, Fe³⁺, K⁺, Lu³⁺, Mg²⁺, Na⁺, Zn²⁺) have been studied.     

Role of topology, nonadditivity, and water-mediated interactions in predicting the structures of alpha/beta proteins

The folding of alpha/beta proteins involves most of the commonly known structural and dynamic complexities of the protein energy landscapes. Thus, the interplay among different structural components, taking into account the cooperative interactions, is important in determining the success of protein structure prediction. In this work we present further developments of our knowledge-based force field for alpha/beta proteins, introducing more realistic modeling of many-body interactions governing the folding of beta-sheets. The model's innovations highlight both specific topological characteristics of secondary structures and the generic nonadditive interactions that are mediated by water. We also investigate how a coarse biasing of the protein morphology can be used to understand the role of heterogeneity in protein collapse. Analysis of the simulation results for three test alpha/beta proteins indicates that the addition of the topological and many-body ingredients to the model helps to greatly reduce the roughness in the energy landscape. Consequently, high quality candidate structures for alpha/beta proteins can be generated from simulated annealing runs, using very modest amounts of computer time.     

Effective charges of polyelectrolytes in a salt-free solution based on counterion chemical potential

The phenomenon of counterion condensation around a flexible polyelectrolyte chain with N monomers is investigated by Monte Carlo simulations in terms of the degree of ionization alpha, which is proportional to the effective charge. It is operationally defined as the ratio of observed to intrinsic counterion concentration, alpha = co/ci. The observed counterion concentration in the dilute polyelectrolyte solution is equivalent to an electrolyte solution of concentration co with the same counterion chemical potential. It can be determined directly by thermodynamic experiments such as ion-selective electrode. With the polyelectrolyte fixed at the center of the spherical Wigner-Seitz cell, the polymer conformation, counterion distribution, and chemical potential can be obtained. Our simulation shows that the degree of ionization rises as the polymer concentration decreases. This behavior is opposite to that calculated from the infinitely long charged rod model, which is often used to study counterion condensation. Moreover, we find that, for a specified line charge density, alpha decreases with an increment in chain length and chain flexibility. In fact, the degree of ionization is found to decline with increasing polymer fractal dimension, which can be tuned by varying bending modulus and solvent quality. Those results can be qualitatively explained by a simple model of two-phase approximation.     

Assessments on energy and efficiency calibration of an alpha spectrometry system using standard sources

Studies and evaluations of the main parameters of a high resolution multi-chamber alpha spectrometer and its full calibration using standard sources of ²⁴¹Am, ²³³U and ²⁴⁴Cm are presented for the validation of the complex method of characterization of an alpha spectrometer dedicated for alpha radioactive concentration measurements of various environmental samples. The resolution and efficiency were determined at all possible source-detector distances for all eight solid state ORTEC ULTRA-AS detectors. In addition, the solid angles associated to different measurement geometries and the repeatability of the results were assessed. A detailed inter-comparison of the results was performed drawing important conclusions regarding the quality of the alpha detector response to the alpha radiation of the standard sources used in measurements.     

Quality control and quality assurance aspects of the routine use of capillary electrophoresis for serum and urine proteins in clinical laboratories

Using capillary electrophoresis (CE) for serum protein electrophoresis, the quality of results begins with monitoring a well-functioning instrument, using scrupulously clean capillaries, well-calibrated methods as well as regular use of an internal quality control material. Quality assurance programs are available in countries such as Australia, United Kingdom, United States, and European countries such as Sweden and Germany. The present commercial control material that is available gives percentages of albumin, alpha 1, alpha 2, beta- and gamma-globulins, the gamma-component being of normal distribution, and not containing any monoclonal protein component. We feel that a quantitative commercial control material containing a monoclonal protein at decision level for treating myeloma patients would be beneficial to all laboratories as a serum protein electrophoresis control, whether the analysis is by CE or agarose gels. The same applies for control material for urinary protein electrophoresis.     

Differential isoelectric focusing properties of crude and purified human alpha 2-macroglobulin and alpha 2-macroglobulin-proteinase complexes

The isoelectric focusing (IEF) properties of human alpha 2-macroglobulin (alpha 2M) and alpha 2M-proteinase complexes from crude and partially purified preparations were studied by column IEF. The average isoelectric point (pI) of the major form was 6.5 for alpha 2M from crude plasma but was 5.3 for purified samples. Following preincubation with either trypsin, chymotrypsin or pancreatic elastase the crude alpha 2M-proteinase complexes displayed pI values ranging from 5.3 to 6.1 and the purified alpha 2M-proteinase complexes ranged from pH 6.0 to 6.1. A comparison of recoveries for focused crude or purified alpha 2M and trypsin-preincubated alpha 2M indicated enhanced recovery for the trypsin-preincubated samples suggesting that the binding of the proteinase enhances the stability of alpha 2M. alpha 2M thus displays column IEF properties which appear to be dependent upon the state of purity of the molecule. These findings are of particular significance to investigators concerned with using expressions of altered alpha 2M electrophoretic patterns for clinical diagnostic purposes in such diseases as multiple sclerosis, diabetes and cystic fibrosis.     

Improved separation of alpha chains of collagen type I, type III, and type V by noninterrupted electrophoresis using thioglycolic acid as a negatively charged reducer

Improved separation of alpha chains of collagen type I (alpha 1 [I]2 alpha 2[I]), type III(alpha 1[III]3), and type V (alpha 1[V]alpha 3[V])was achieved by noninterrupted sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a negatively charged reducer, thioglycolic acid. The thioglycolic acid, added to the running buffer of the cathodic reservoir, in the middle of electrophoresis quickly migrated in the gel anode, reducing interchain disulfide linkages in collagen type III and dissociating it into its alpha chain monomer, alpha 1[III], without an interruption of electrophoresis. The alpha chain, alpha 1[III], migrated more slowly than the alpha 1 [I] and alpha 2[I] chains of collagen type I, resulting in an excellent separation of alpha 1[III] from alpha 1[I]. The mobility of alpha 1[III] could be controlled by varying the time of thioglycolic acid addition to the running buffer. This enabled us not only to separate alpha 1[III] from alpha 1[I] and alpha 1[V], but also to precisely quantitate these alpha chains, even at low protein loading of mixed samples.     

Determination of radionuclidic impurities in <Superscript>99m</Superscript>Tc eluate from <Superscript>99</Superscript>Mo/<Superscript>99m</Superscript>Tc generator for quality control

Technetium-99m is the principal radioisotope used in medical diagnostics; radionuclidic impurity is the major concern of its quality. This work presents a analytical method for sequential determination of all radionuclidic impurities listed in pharmacopoeia including gamma emitters, alpha emitters, ⁸⁹Sr and ⁹⁰Sr. Radioactive decay for removal of ^99mTc, ion exchange and extraction chromatography for removal of ⁹⁹Mo and ⁹⁹Tc are effective for separation of interferences. Gamma spectrometry, LSC with alpha/beta discrimination, and Cherenkov counting using LSC are sensitive methods for measurement of the impurity radionuclides. The detection limits of this method are well meet the requirement of the quality control according to the limitation of the pharmacopoeia.     

Estimation of the persistence length of DNA from the torsion elastic constant and supercoiling free energy: effect of ethylene glycol

Two different methods are proposed to estimate the persistence length ( P) of DNA from the measured torsion elastic constant (alpha) and the twist energy parameter ( E T ) that governs the supercoiling free energy. The first method involves Monte Carlo simulations and reversible-work calculations of E T for model DNAs that possess the measured alpha and selected trial values of P. Comparison of the computed E T values with the experimental value allows estimation of P (or equivalently the bending elastic constant (kappa beta)) by interpolation. A far simpler, though less accurate, alternative is to solve a previously conjectured analytical relation connecting E T , alpha, kappa beta (or P), and an unknown "constant" ( B). The present simulations are used to ascertain the optimum value of B and to assess the validity and accuracy of that relation. Within the simulation errors, P values obtained from the measured alpha and E T via this analytical expression agree with those determined from the simulations and E T values reckoned from the input alpha and kappa beta by this analytical expression agree with the corresponding simulated values. Although B is found to be insensitive to variation in alpha, it appears to decline slightly with increasing kappa beta. The original analytical expression is modified to take this apparent variation of B with kappa beta into account. By using this modified analytical relation to estimate P (from the measured alpha and E T ) or E T (from the input alpha and kappa beta), much closer agreement is obtained respectively with the values of P or E T obtained from the simulations. As specific examples, these methods are applied to determine P in 0 and 20 w/v % ethylene glycol, which has been shown to induce a structural transition in duplex DNA.     

2.3 Wood pulp manufacturing and quality characteristics

Cellulose acetate being important in the fiber and textile industries is usually prepared from high quality cellulose such as cotton linters and wood pulps with an alpha cellulose content of more than 95%. In this section, therefore, wood pulps and cotton linters appropriate for cellulose acetate production were discussed in their chemical and physical properties so as to use them judiciously as natural raw materials for cellulose acetate production.     

Mass fragmentographic determination of prostaglandin F2 alpha in human and rabbit urine

Analysis of prostaglandin F2 alpha (PGF2 alpha) in urine is a useful indicator of renal prostaglandin synthesis. A mass fragmentographic method for PGF2 alpha analysis in human urine was developed using [3,3,4,4-2H4]PGF2 alpha as an internal standard and carrier. PGF2 alpha was extracted from urine (20 ml) with chloroform, purified by preparative thin-layer chromatography and converted to the methyl ester trimethylsilyl ether before analysis by gas chromatography--mass spectrometry. The specificity of the urine analysis was demonstrated by retention time and the use of two pairs of fragments m/e 494/498 and 513/517 with the same results. The coefficient of variation for duplicate analysis averaged 12.6%, n = 17. Urine from recumbent women contained 4.9 +/- 2.6 (S.D.) ng/ml or 4.1 +/- 1.0 ng PGF2 alpha per mg creatinine (n = 10) with little diurnal variation. Male urine contained 5.0 +/- 2.7 (S.D.) ng/ml or 3.7 +/- 2.1 ng/mg creatinine (n = 10). Similar concentrations were found in boys and in girls. These observations indicate that urinary PGF2 alpha originates from the kidneys with little contribution from the male accessory sexual glands. This method can also be applied to analysis of PGF2 alpha in rabbit urine.     

Dimethylisopropylsilyl ether derivatives in gas chromatography-mass spectrometry of some prostanoids. Application to the microdetermination of 15-ketoprostaglandin F2 alpha formed by enzymatic conversion of PGF2 alpha in vitro

Treatment of 15-ketoprostaglandin F2 alpha (15-keto-PGF2 alpha) with ethereal diazomethane at -78 degrees C provided only the expected methyl ester (ME), without the formation of the pyrazoline adduct. The electron-ionization mass spectrum of the dimethylisopropylsilyl (DMiPS) ether derivative of 15-keto-PGF2 alpha ME showed the molecular ion, and the characteristic fragment ion of [M-43]+ was of high abundance. The appearance of these ions in the high-mass region made it possible to determine trace amounts of 15-keto-PGF2 alpha in biological specimens without any interference from endogenous substances. The detection limit for the DMiPS ether derivatives of 15-keto-PGF2 alpha ME was 12 pg (signal-to-noise ratio = 10). The method was applied to the analysis of 15-keto-PGF2 alpha obtained by the enzymatic conversion of PGF2 alpha with 15-hydroxyprostaglandin dehydrogenase in vitro.     

Determination of prostaglandins and thromboxane in whole blood by high-performance liquid chromatography with fluorimetric detection

A highly sensitive and specific assay for the quantitation of prostaglandins (PGs) such as PGE1, PGE2, PGF1 alpha, PGF2 alpha, 6-keto-PGF1 alpha, and including thromboxane B2, is described. The method involves the addition of PGF1 alpha and PGE1 as the internal standards, extraction from whole blood and purification by silica gel column chromatography. Following conversion into the methoximes, purification by reversed-phase chromatography and esterification with panacyl bromide, samples are analysed by high-performance liquid chromatography with fluorimetric detection. The lower limit of detection of the eicosanoids 6-keto-PGF1 alpha, thromboxane B2 and PGF2 alpha in blood is ca. 50 pg/ml and that of PGE2 is 100 pg/ml. Assay linearity is demonstrated over a range from 60 pg to 60 ng of eicosanoid injected. The method allows simultaneous assessment of prostaglandins and thromboxane extracted from complex biological fluids at picogram levels.     

Kinetics of cross-nucleation between polymorphs

We report the first kinetic measurement of cross-nucleation between polymorphs, a newly discovered phenomenon important to the theory and control of crystallization. d-Mannitol crystallized from its melt first as the least stable delta polymorph and then as the second least stable alpha polymorph, with alpha nucleating on delta. The kinetics of cross-nucleation was determined from the frequencies of alpha nuclei appearing on delta spherulites, the distances between alpha and delta nuclei, and the growth rate of the delta spherulite. The presence of poly(vinylpyrrolidone), a noncrystallizing, melt-miscible additive, increased the rate of cross-nucleation.     

Synthesis of PDK, a novel porphyrin-linked dicarboxylate ligand

A novel trinucleating ligand system H4(PDK), for porphyrin-based diamine bis(Kemp's triacid)imide, was constructed by using two molecules of Kemp's triacid and one molecule of porphyrin as building blocks. The dimeso-substituted octaalkylporphyrin unit, carrying bromomethyl groups at the ortho positions of two trans-positioned meso-phenyl groups, was synthesized from (3,3'-diethyl-4,4'-dimethyl-2,2'-dipyrrolyl)methane and (alpha-bromo-o-tolualdehyde. The structures of both of the two atropisomers (alpha,alpha- and alpha,beta-) of bromoporphyrin, H2(alpha,alpha-BP) and H2(alpha,beta-BP), were determined by X-ray crystallography, with the alpha,beta-isomer as the free base form and the alpha,alpha-isomer as the zinc complex. Both the alpha,alpha- and alpha,beta-isomers of the bromomethyl porphyrins were converted to their aminomethyl derivatives, H2(alpha,alpha-AP) and H2(alpha,beta-AP), through the corresponding imidoporphyrin intermediates, H2(alpha,alpha-IP) and H2(alpha,beta-IP), by the Gabriel synthesis. The alpha,alpha- and alpha,beta-aminoporphyrins were coupled with Kemp's triacid anhydride-chloride to form H4(alpha,alpha-PDK) and H4(alpha,beta-PDK), respectively. Unlike the alpha,beta-isomer, the structure of which was determined by X-ray crystallography for the zinc complex, H4(alpha,alpha-PDK) has a remarkable and complicated solvent-dependent 1H NMR spectrum that suggests the existence of hydrogen bonding interactions between two convergent, tethered Kemp's triacid units, as predicted in a modeling study. The convergent feature is essential for the target ligand H4(alpha,alpha-PDK) to form trinuclear metal complexes with a bis(carboxylato) dimetallic unit sitting above a metalloporphyrin ring.     

A preliminary study of gross alpha/beta activity concentrations in drinking waters from Albania

A pilot study involving screening measurements of gross alpha/beta activity concentration in drinking water was performed in 12 cities with the highest population density in Albania. The aim of this study was to develop a first insight regarding the radiological quality of drinking and bottled water supplies. The tap and bottled water samples investigated are acceptable for consumption, complying with the WHO recommendations for drinking water. The average gross alpha and beta activity concentrations were \( 36_{ - 18}^{ + 37} \) and \( 269_{ - 150}^{ + 337} \)  mBq/L, respectively in tap waters. While for bottled water the gross alpha and beta activities were respectively \( 39_{ - 23}^{ + 55} \) and \( 220_{ - 132}^{ + 336} \)  mBq/L. The data obtained can provide information for authorities regarding the quality of drinking water and a baseline for future contaminations.     

Effect of doping an organic molecule ligand on TGS single crystals

Good quality single crystals of thiourea-doped triglycinesulphate (TuTGS) a new semiorganic nonlinear optical (NLO) crystal has been successfully grown from aqueous solution by slow evaporation method. The solubilities under various solvents in different proportions have been studied. The structural characterization of the grown crystals was carried out by X-ray diffraction. The grown crystals were subjected to FTIR and Raman analyses for vibrational assignments. The optical absorption coefficient alpha was analysed and interpreted to be allowed in the direct transition. The values of allowed direct energy gap (Eg) for undoped and doped crystals were calculated. It was found that Eg values were decreased with organic molecule doping. The powder technique of Kurtz and Perry confirm the NLO property of the grown crystal.     

Electrophoretic purification of the alpha and beta subunits of phosphorylase kinase and evidence in support of the deduced amino acid sequences

A simple, rapid sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) method is presented for isolating the alpha, alpha' and beta subunits of rabbit muscle phosphorylase kinase. The SDS-PAGE procedure can yield milligram amounts of alpha and beta from a single preparative gel and also allows isolation of the alpha' isozyme free of alpha. Notably the method provides the purified subunits in a form amenable to structural analysis. Edman degradation of alpha and alpha' reveal identical NH2-terminal structures. Amino acid analysis of the electrophoretically purified alpha and beta subunits are in good agreement with their deduced primary structures. The amino acid sequence of 488 residues in alpha and 713 residues in beta were determined by gas phase Edman degradation. The data support the recently deduced primary structures of alpha (Zander et al., Proc. Natl. Acad. Sci. USA, 1988, 85, 9381-9385).