L-arginine Phosphate Research Articles

Study of laser induced damage threshold and effect of inclusions in some nonlinear crystals

The paper reports the comparative studies on the laser-induced single-shot and multiple-shot surface damage thresholds of nonlinear crystals, viz. Urea, 3-methyl-4-nitropyridine-1 oxide (POM), l-arginine phosphate (LAP) and β-barium borate (BBO) crystals. The measurements were made using radiation of 1064 nm and its second harmonic generation, i.e. 532 nm from a Q-switched Nd:YAG laser of pulse width 10 ns. In addition, the effect of Na + impurity incorporated during growth in BBO crystal in different concentration (wt.%) has also been studied, and attempted to be correlated with various factors. We also measured the absorption coefficients of these crystals at different wavelengths. The Scanning Electron Microscope coupled with Energy Dispersive X-Ray Analyzer (SEM-EDX) has been employed to study the inclusions/impurities present in the crystals.

Growth and investigation of new non-linear optical crystals of LAP family

The possibility of preparing new analogs of L-arginine phosphate monohydrate, (LAP), has been investigated. Single crystals of the compound L-Arg·HCOOH, which had earlier been obtained in powdered form, were successfully grown during the course of this investigation. In addition, we have found that there is a class of compounds having the Arg·2Ax composition, (where Ax is one of several inorganic or organic acids). Such compounds (Arg·2HIO 3, Arg·2HNO 3, Arg·2H 3PO 4, Arg·2HF, Arg·2HCl·H 2O, and Arg·2HBr·H 2O) have been synthesized and single crystals grown. The crystals grown in this investigation were studied by IR and X-ray diffraction methods. The influence of the different amino acid groups on crystal symmetry and the influence of this symmetry on non-linear optical properties are discussed.

Experimental evidence for the unusual damping parameter in l-arginine phosphate monohydrate single crystal

The longitudinal ultrasonic attenuation and velocity of l-arginine phosphate monohydrate (LAP) single crystal were investigated at 11.6, 15, and 30 MHz from 160 to 300 K during heating. An internal friction peak was found in all experiments. The frequency dependence of this peak indicates that it is associated with dislocation resonance damping. Although it is generally believed that the damping parameter B in the vibrating-string model of dislocation damping is approximately proportional to the temperature in metals, our results indicate that in LAP single crystal, parameter B can be expressed as B ∝ τ = me –n/T, where τ is the relaxation time, T is the temperature, and m and n are positive constants.

Physical, chemical and optical properties of aqueous L-arginine phosphate (LAP) solution

The mathematical modelling of the solution growth of high quality single crystals requires a good understanding of the fluid properties. In addition to the physical and mechanical properties a detailed knowledge of the optical parameters is required to study the dynamics of the crystal growth process. Measurements of polarizability, refractive index, optical dispersion, solubility, pH, viscosity, and density were performed on aqueous L-Arginine phosphate (LAP) solutions. The index of refraction was measured with an Abbe refractometer at four different wavelengths. Optical dispersion was calculated using the Cauchy's equation. Effects of the density and kinematic viscosity of the LAP solution are discussed in terms of the dimensionless Grashof and Reynolds number allowing a better understanding of the benefits of operating under the ‘micro-g’ conditions of space for the solution growth of single crystals. The Cauchy's formula and Sellmeier formula of the refractive index have been used to determine both the gradients dn/dc and dn/dT as a function of wavelength and the polarizability of the LAP solution. The polarizability of the LAP crystal, α2, was found to be 14.50 cm3/mol and this value was in good agreement with experimental data obtained and analyzed using the well-known Lorentz-Lorenz formula.

Habit modification of potassium acid phthalate (KAP) single crystals by impurities

Nonlinear optical materials potassium dihydrogen phosphate (KDP), urea and l-arginine phosphate (LAP)-doped KAP crystals were grown by the slow cooling method. The LAP-doped crystals show pronounced habit modification compared to KDP and urea doping. The effect of these impurities on growth kinetics, surface morphology, habit modification, structure, optical and mechanical properties have been studied. Among the three impurities, urea doping yields high mechanical stability and optical transmission and for KDP and LAP doping there is a decrease in optical transmission.

Investigations on the Nucleation Kinetics of L-Arginine Phosphate single crystals

The nucleation parameters, such as radius of the critical nucleus and critical free energy change have been evaluated for LAP single crystals. The interfacial tension determined by conducting the induction period measurements has been used for the evaluation of nucleation parameters. The determined interfacial tension is found to be comparable with theoretical literature values.

Growth and characterisation of L-arginine phosphate family crystals

In order to improve the device characteristics of L-arginine phosphate (LAP) family of crystals, metals doping with oxides of copper and magnesium were examined. Mg-doped crystals enhance the growth along the c-axis; X-ray powder diffraction patterns were used to calculate the lattice parameters of the crystals. Fourier transform infra red (FTIR) spectroscopy and thermal analysis (DTA, TGA) were performed to study the molecular vibrations and thermal behaviour of the crystals, respectively. Mechanical characterisations such as micro-hardness studies on (1 0 0) and (0 1 0) planes were also carried out. The weight percentage of the doped copper and magnesium were calculated by atomic absorption spectroscopy (AAS).

A simple, low-cost laser interferometry technique for singlecrystal growth

Interferometry is an essential field of optical metrology and is adapted in many applications in optics, crystal growth and industry. The crystal growth rate is one of the critical parameters for the growth of optical-quality single crystals. A laser interferometry technique has been developed and applied successfully for crystal growth rate measurement from solution. A He-Ne laser at the wavelength of 633 nm with an output power of 1.5 m W was used in this experiment. The beam was incident on the crystal growing from solution. As the crystal is growing, the path length of the front and back surface reflected beam changes and hence the phase factor of the detector output signal changes continuously. This phase change is directly related to the growth of crystal. The growth rate of the L-arginine phosphate crystal was found to be 6.5 nm s−1. The resolution of the laser interferometry was & deg; which corresponds to 5.02 nm.

Secretion of a variant of human single-chain urokinase-type plasminogen activator without an N-glycosylation site in the methylotrophic yeast, Pichia pastoris and characterization of the secreted product.

Human single-chain urokinase-type plasminogen activator without an N-glycosylation site (scu-PA-Q302) was produced in the methylotrophic yeast, Pichia pastoris using the shortened prepeptide sequence of a fungal aspartic proteinase, Mucor pusillus rennin (MPR). The level of urokinase-type plasminogen activator (u-PA) immunoreactive material in YPM medium was 0.47 mg/l; however, most of the secreted product had been processed to smaller polypeptides. The N-terminal amino acid sequence of major species was identical to that of the low molecular weight two-chain u-PA. Some approaches to minimizing the proteolysis of scu-PA-Q302 were attempted. Addition of Triton X-100, L-arginine and ammonium phosphate to the YPM medium minimized the proteolysis of scu-PA-Q302 and increased the yield of immunoreactive material to approximately 5 mg/l. Use of proteinase A- or proteinase B-deficient strains of yeast did not reduce the degradation. Co-expression of scu-PA-Q302 and urinary trypsin inhibitor resulted in partial reduction of the major species of proteolysis. Scu-PA-Q302 was purified from the culture supernatant of the improved medium by two successive chromatographies on Phenyl-Sepharose and S-Sepharose. The purified protein had a molecular weight of 47 kDa. It did not contain detectable N-linked oligosaccharides, but contained O-linked oligosaccharides attached to the light chain. N-terminal amino acid sequencing of the purified preparation showed that the shortened prepeptide sequence of MPR was correctly processed by the Pichia yeast. Scu-PA-Q302 closely resembles natural scu-PA with respect to its enzymatic activity against the chromogenic substrate S-2444 and its in vitro fibrinolytic properties.

Letter refractive index variation measurements of fluids using common-path Zeeman interferometry

A common-path Zeeman interferometry technique has been deveioped and applied for the measurements of refractive index gradients of the fluids to an accuracy of Δn=9.4 × 10−9. The Zeeman interferometry technique has over 100 times better resolution than the other interferometry techniques. A linear refractive index profile of the solution at the interface of the growing L-arginine phosphate crystal from solution was measured successfully using a scanning Zeeman interferometry technique.

Investigation of Some New Nonlinear Optical Crystals by Means of NQR, IR and X-Ray Diffraction Methods

Abstract Some new analogues of the nonlinear optical crystal L-arginine phosphate monohydrate (LAP) (Arg • HIO3 , Arg • 2HIO3 , Lys • HIO3 , Lys • 2HIO3 , Lys • 3HIO3 , Bet • 3HIO3) were obtained and investigated by means of IR, NQR, X-ray diffraction and SHG methods. The importance of this class of crystals for revealing new nonlinear optical crystals is pointed out.

Capillary electrophoresis analysis of nitric oxide synthase related metabolites in single identified neurons.

Intracellular concentrations of L-citrulline (Cit) and its metabolites are related to nitric oxide synthase (NOS) activity, an enzyme producing the intercellular messenger NO in animal tissues including the nervous system. A capillary electrophoresis system using laser-induced fluorescence detection is described, and methods are developed to monitor the levels of L-arginine (Arg), Cit, and related molecules in identified neurons of the marine slugs, Pleurobranchaea californica and Aplysia californica. The limits of detection for Arg, Cit, L-arginino-succinate, L-ornithine, and L-arginine phosphate range from 50 amol to 17 fmol (5 nM to 17 microM in the neurons under study); these detection limits are significantly lower than actual intracellular levels of the metabolites, allowing the direct assay of single cells. The levels of NOS metabolites in individual neurons varied form 6 (Arg) and 4 mM (Cit) in putative NOS-containing neurons down to < 1 microM (undetectable) levels in many putative NOS-negative cells. The Arg/Cit ratio is independent of cell volume, correlates with NADPH-diaphorase staining, and appears to be a characteristic parameter for the presence of NOS activity in identified neurons.

Optical heterodyne interferometry technique for solution crystal growth rate measurement

A noncontact optical heterodyne technique was implemented for in situ measurement of crystal growth rate from solutions. A two- frequency Zeeman laser with a total output power of 1 mW (each polar- ized component is 0.5 mW) was used at 633 nm and is composed of two frequencies n 1 and n 2 that are collinear but polarized orthogonally to each other and separated by precisely 250 kHz. The sensitivity of the system was found to be 0.77 nm. This value is larger than the theoretical resolution limit of 0.065 nm because of the noise associated with the vibrations. The critical factors of the heterodyne technique for the moni- toring of solution crystal growth have been studied. The growth rate of L-arginine phosphate crystal was 6.1560.13 nm/s (0.53 mm/day) at the solution temperature of 28.2°C and seed crystal temperature of 26.0°C. This is the first experiment in which the heterodyne technique has been applied for real-time in situ measurement of crystal growth rate. © 1998 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(98)02302-2)

Assay of NOS activity by the measurement of conversion of oxyhemoglobin to methemoglobin by NO.

AbstractNitric oxide synthase (NOS) catalyzes the conversion of L-arginine, molecular oxygen, and nicotinamide adenine dinucleotide phosphate (NADPH) to NO, citrulline, and NADP+ (reviewed in ref. 1). This chapter describes the measurement of NOS activity by utilizing the conversion of oxyhemoglobin to methemoglobin by NO while monitoring the absorption difference between the wavelengths 401 and 421 nm or at just 401 nm. This assay was first described by Feelisch and Noack (2) and has since been modified to allow not only the measurement of NOS activity in vitro but also the degree of in vivo inhibition of neuronal (n) NOS (and also possibly endothelial (e) NOS) by ex vivo analysis after the administration of slowly dissociating inhibitors such as Nω-nitro-L-arginine (L-NNA) and its methyl ester, L-NAME (3,4). Using the protocol described, this technique is sensitive (limit of detection approx 20 pmol/min per g tissue), specific for NOS in conjunction with the use of NOS inhibitors, applicable to most preparations (with the exception of samples containing large amounts of hemoglobin) and suitable for continual monitoring.KeywordsMethyl EsterFlavin Adenine DinucleotideNicotinamide Adenine Dinucleotide PhosphateSodium DithioniteFlavin Adenine DinucleotideThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Efficient stimulated Brillouin scattering in the organic crystal deuterated L-arginine phosphate monohydrate

A stimulated Brillouin scattering phase-conjugate mirror with the organic nonlinear optical crystal deuterated l-arginine phosphate monohydrate has shown a reflectivity of more than 80% at 1064 nm. We demonstrate the correction of a deliberate aberration for a 10-Hz Nd:YAG laser by this crystal.

High-energy operation of a stimulated Brillouin scattering mirror in an l-Arginine phosphate monohydrate crystal

An organic l-Arginine phosphate monohydrate (LAP) crystal showed a much lower stimulated Brillouin scattering (SBS) threshold at 1.06-mum wavelength than fused silica and a higher SBS reflectivity of approximately 65%, which is limited because of its absorbance. The reason LAP crystal has a high damage threshold at Q -switched pulse operation is due to SBS backward reflectance. The LAP crystal is interesting not only as a frequency converter but also as a phase-conjugated SBS mirror for all solid-state high-energy lasers because of its high SBS gain coefficient.

AFM study of etching of cleaved {1 0 0} faces of L-arginine phosphate monohydrate single crystals I. Dislocation etch pits and step bunching

The formation of dislocation etch pits and the process of coalescence of dissolution steps composing the walls of dislocation etch pits on the etched {1 0 0} cleavage faces of L-arginine phosphate (LAP) single crystals was studied by using atomic force microscopy (AFM). The results show that (1) etch pits at edge and screw dislocations are formed by repeated two-dimensional nucleation mechanism, (2) the values of different slopes of etch pits in regions close to dislocation lines are due to differences in the stress fields of dislocations producing the etch pits, and that (3) the process of step bunching is statistical in nature.

AFM study of etching of cleaved {1 0 0} faces of L-arginine phosphate monohydrate single crystals II. Two-dimensional nucleation, formation of spiral elevations and decoration of dissolution layers

Observations on the formation of two-dimensional (2D) etch pits, the decoration of dissolution steps and the formation of dissolution spiral elevations on the etched {1 0 0} cleavage faces of L-arginine phosphate (LAP) single crystals made by using atomic force microscopy (AFM) are described and discussed. It was found that spiral elevations at the points of emergence of screw dislocations are formed during dissolution by the retreating of their elementary steps around decorated centres, and that there are gradients in undersaturation on the surface in the vicinity of spiral elevation centres, the maximum undersaturation being at spiral centres.

Experimental determination of metastable zone width, induction period and interfacial energy of LAP family crystals

Experimental determination of the metastable zone width and induction period on l-arginine phosphate (LAP) family crystals are presented. To delay the microbial growth, the use of a new additive, sodium azide (NaN 3) has been proposed. Partial substitution of sulphate for phosphate has been carried out. The effect of substitution of sulphate and addition of sodium azide on the nucleation parameters has been studied. The presence of sodium in the crystal has been quantified by the inductively coupled plasma (ICP) analysis. The results of the interfacial energy calculation are also presented.

Observations of cleavage steps, slip traces and dislocation hollow cores on cleaved {100} faces of l-arginine phosphate monohydrate single crystals by atomic force microscopy

The results of an atomic force microscopy study of the nature of cleavage steps, observation of slip traces and formation of hollow cores at the centres of dislocations on the {100} faces of l-arginine phosphate monohydrate (LAP) single crystals grown from aqueous solutions are described and discussed. It was observed that: (1) most of the cleavage steps and all the slip traces are of elementary height, a = 1.085 nm; (2) the origin of a cleavage step may or may not have a hollow core; and (3) close to its origin, the curvature of a cleavage step may be positive or negative or may change from positive to negative. The results suggest that slip traces observed on the cleaved surfaces of LAP are formed during the cleavage process while the rounding and the rearrangement of elementary cleavage steps take place immediately after the occurrence of cleavage. Analysis of the results also shows that the dislocations responsible for the origin of hollow cores always represent a stress field state corresponding to a trapped solution of different local interface supersaturations.