Disodium Guanosine Research Articles

Dissolution and Growth Kinetics and the Rate-Controlling Step in Transformation of Amorphous to Crystalline Phase Using Antisolvent Crystallization

The kinetics of the formation of amorphous disodium guanosine 5′-monophosphate and its transformation to the heptahydrate phase were studied under various operating conditions using in situ Raman and focused beam reflectance measurement (FBRM). Supersaturation, solvent composition, feed concentration, addition rate, and viscosity were shown to affect the rate-determining steps of the transformation. The rate-controlling mechanisms in the overall kinetics have been confirmed. The observation of the slurry viscosity of the suspension of the amorphous phase shows the option to observe the phase transformation. The transformation process was affected by the dissolution, growth, and supersaturation in which the rate-controlling step was divided into two sections, such as the initial and later sections of the transformation. The overall rate constants were determined by combining the constants of the dissolution rate and the growth rates of each section. In situ Raman spectroscopy examination of the concentration of solution and solids can determine the rate-limiting processes during the transformation. The zero-order, first-order, and surface reaction equations as kinetic equations are highlighted and compared for the dissolution of the amorphous solids and the growth of the heptahydrate crystals. The dissolution of the amorphous (metastable form) and the growth of the heptahydrate (stable form) were found to be best fitted to the zero-order kinetic model. In particular, the variation of particle size distribution over time can give the rate-determining steps. These results suggest that the data measured by Raman spectroscopy and FBRM can be successfully coupled into a dissolution and growth model to further grasp and interpret the phase transformation. A dissolution rate-controlling step was dominated by a pattern in which both supersaturation and amorphous dissolution decreased simultaneously, and the growth rate-controlling step was shown in a pattern in which either supersaturation or amorphous dissolution was constant. Furthermore, the growth of heptahydrate crystals at a viscosity of the suspension with the amorphous solids below 70 cp and the dissolution of the amorphous solids above it can be used as the key determinant. Using the method developed and the kinetic constants obtained in this work, it is possible to create an appropriate control strategy to produce the desired form in the final product.

Finding Conditions to Process Hydrate Crystals and Amorphous Solids of Disodium Guanosine 5′‐Monophosphate by an Antisolvent Crystallization Process

AbstractA screening of amorphous, heptahydrate, and tetrahydrate forms of disodium guanosine 5′‐monophosphate is investigated using an antisolvent crystallization process with the aim to selectively produce each solid form. The concentrations of the solution and solid forms are monitored by in situ Raman spectroscopy using a calibration tool. Particle sizes and particle counts are measured with elapsed time by a focal beam reflection measurement. Concentrations of amorphous and hydrates phases are determined using in‐line measurement techniques. The variables studied are temperature, initial concentration, addition rate, and solvent fraction. The results demonstrate that transformation from amorphous to hydrate forms consists of four stages, which are the nucleation of the amorphous form, predissolution of amorphous form, the nucleation of hydrate crystal and dissolution of amorphous solid, and the growth of hydrate crystal. The rate‐controlling step, in this case, is the dissolution of amorphous form. Transformation between heptahydrate to tetrahydrate crystals is a nucleation‐growth‐controlled step. It is possible to obtain selectively the solid forms of disodium guanosine 5′‐monophosphate by referring to the supersaturation and solubility data.

PH-dependent oiling-out during the polymorph transformation of disodium guanosine 5′-monophosphate

A typical oiling-out process in the binary phase with FBRM patterns and an online picture.

Thermodynamic Study on the Amorphous Form and Crystalline Hydrates Using in Situ Raman and FBRM

AbstractThe solubilities and maximum supersaturation concentrations of an amorphous and the crystalline tetrahydrate and heptahydrate solids of disodium guanosine 5'‐monophosphate (GMP) in water‐methanol mixtures were measured in situ by Raman spectroscopy and focused beam reflectance measurement. The distinct Raman peaks of the amorphous form, crystalline hydrates, solution, and solvent were used for measurements of solubility and maximum supersaturation. Above 45 °C and at methanol fractions of 0.15–0.90, the tetrahydrate was the stable form, while below 40 °C and at methanol fractions of 0.15–0.60, the heptahydrate was the stable form. Especially, the tetrahydrate was stable in the methanol fraction > 0.7 at the temperature investigated. The solubility and supersaturated concentration values can be used to selectively produce amorphous, tetrahydrate, and heptahydrate solids of GMP by anti‐solvent crystallization.

Surface functionalization of graphene oxide by disodium guanosine 5′-monophosphate and its excellent performance for lipase immobilization

Abstract In order to solve the toxic and hazardous issues of the agents in the chemical reduction process of graphene oxide (GO), disodium guanosine 5′-monophosphate (GMP-2Na) was used as an ideal reducing agent for the synthesis of functionalized GO (FGO) for lipase immobilization. At the condition of low amount adsorption of GMP-2Na indicated by the N1s spectra of X-ray photoelectron spectroscopy (XPS), the C/O atomic ratio of the FGO increased from 2.09 to 3.12, indicating the reduction of GO. As the amount of GMP-2Na increased, the intensity of the characteristic peak of GO in the XRD pattern decreased, and the I D /I G peak intensity of Raman spectra increased during the functionalization process. It was found that when the concentration of GMP-2Na is 0.20 mg/mL, the degree of hydrophobicity of FGO is conducive to the formation of optimal conformation of lipase. After immobilization, the activity of the immobilized enzyme reaches twice the value of free enzyme. At the same time, the protein loading reaches to 600 mg/g. The immobilized enzyme showed enhanced durability since no obvious decrease was observed after incubation for 8 h at pH 6.0 and pH 7.0. After storage for 35 days, the activity of GO-G@ enzyme was 54.47% higher than that of free enzyme. GO reduced by GMP-2Na provides a possibility to obtain a highly efficient lipase immobilization carrier.

Crystal structure and sequential dehydration transitions of disodium guanosine 5'-monophosphate tetrahydrate.

Disodium guanosine 5'-monophosphate was reported previously to crystallize as both the tetrahydrate and the heptahydrate. We herein report a determination of the molecular and crystal structures of the title tetrahydrated salt, 2Na+·C10H12N5O8P2-·4H2O. It was found that the structure differs markedly from that of the heptahydrate, but greatly resembles that of disodium deoxyguanosine 5'-monophosphate tetrahydrate. The C2'-O2'H moiety of ribose is surrounded by hydrophilic moieties and is disordered over two sites. The sugar puckering mode is O4'-endo-C1'-exo at both sites and the conformation around the C4'-C5' bond is gauche-trans. Powder X-ray diffraction and thermal analyses revealed that the temperature-controlled transition from the tetrahydrate to the anhydride proceeded through three intermediate phases between 40 and 60 °C at 0% relative humidity. Large induction periods were observed.

Transformation of microstructure and phase of disodium guanosine 5′-monophosphate: Thermodynamic perspectives

Abstract Microstructure and phase transformation of disodium guanosine 5′-monophosphate (5′-GMPNa 2 ) are extremely important for controlling the process and understanding the mechanism of crystallization. In this work, the thermodynamic properties of polymorphous 5′-GMPNa 2 especially the solubility were studied, the solubility results show that 5′-GMPNa 2 is more soluble in ethanol–water (E–W) than in isopropanol–water (I–W). The amorphous form of 5′-GMPNa 2 is more soluble than the crystalline form at the same mole fraction and temperature. Meanwhile, the crystalline forms and morphologies of the residual solids were characterized by PXRD and SEM. The results indicate that solid forms of 5′-GMPNa 2 transformed spontaneously from amorphous to crystalline when the ethanol proportion is ≥ 20%. In addition, increasing the pH facilitates the dissolution of 5′-GMPNa 2 and helps to maintain the crystalline form. The associated Gibbs free energy values were calculated to verify the trend of transformation from amorphous to crystalline 5′-GMPNa 2 . These results should help to guide the industrial crystallization process and to obtain the crystalline form of 5′-GMPNa 2 .

Temperature and pressure limits of guanosine monophosphate self-assemblies

Guanosine monophosphate, among the nucleotides, has the unique property to self-associate and form nanoscale cylinders consisting of hydrogen-bonded G-quartet disks, which are stacked on top of one another. Such self-assemblies describe not only the basic structural motif of G-quadruplexes formed by, e.g., telomeric DNA sequences, but are also interesting targets for supramolecular chemistry and nanotechnology. The G-quartet stacks serve as an excellent model to understand the fundamentals of their molecular self-association and to unveil their application spectrum. However, the thermodynamic stability of such self-assemblies over an extended temperature and pressure range is largely unexplored. Here, we report a combined FTIR and NMR study on the temperature and pressure stability of G-quartet stacks formed by disodium guanosine 5′-monophosphate (Na25′-GMP). We found that under abyssal conditions, where temperatures as low as 5 °C and pressures up to 1 kbar are reached, the self-association of Na25′-GMP is most favoured. Beyond those conditions, the G-quartet stacks dissociate laterally into monomer stacks without significantly changing the longitudinal dimension. Among the tested alkali cations, K+ is the most efficient one to elevate the temperature as well as the pressure limits of GMP self-assembly.

Solution-Mediated Polymorphic Transformation: From Amorphous to Crystals of Disodium Guanosine 5′-Monophosphate in Ethanol

Solvent-mediated transformation of disodium guanosine 5′-monophosphate (5′-GMPNa2) from amorphous to hydrated crystal phases was studied. The SMT process is dominated by the dissolution of the amorphous form and nucleation and growth of the crystal polymorph. The kinetic estimation based on population balance equation was carried out according to experimental data, including polymorphic fraction in the solid phase, solute concentration, and crystal size distribution. Furthermore, independent seeded batch experiments were carried out to estimate the kinetic parameters. The experimental data showed that the nucleation and growth of the crystal polymorph occurred shortly after the dissolution of the amorphous form. The estimated growth, nucleation, and dissolution rates indicated that the solution-mediated transformation was governed by the nucleation and growth of crystal polymorph. We believe that the results hold great importance toward understanding the transformation process of 5′-GMPNa2, which provides...

Solvent effects on nucleation of disodium guanosine 5′-monophosphate in anti-solvent/water mixtures

The influence of the solvent on the nucleation of disodium guanosine 5′-monophosphate (GMPNa2) in eight methanol (ethanol)–water mixtures and at three supersaturation levels at 293.15 K was investigated. The interfacial free energy, the critical size for nucleation, and the number of molecules were calculated using equations re-derived from the classical nucleation theory. GMPNa2 nucleation involves not only a primary nucleation process but also the conversion from a homogeneous to a heterogeneous process. The transformation experiment indicated that the nucleation of GMPNa2 follows the two-step model. A surface entropy factor (fb) was proposed to relate the solvent composition and interfacial free energy in order to explain the solvent effects on the nucleation process. Although the fb values can be used to judge the crystal growth mode, nucleation and growth cannot be separated, since pure primary nucleation does not occur for this compound. The fb values clearly increased with increasing solvent content and decreasing supersaturation. For the homogeneous process in a methanol–water system, regular crystals can be formed only when fb > 5, regardless of the supersaturation, as was observed for solvent contents of 40 mol% and 30 mol% (S = 1.83 and 1.70, respectively). These results can help select a suitable solvent system and its composition during anti-solvent crystallization.

Determination of Metastable Zone Widths and the Primary Nucleation and Growth Mechanisms for the Crystallization of Disodium Guanosine 5′-Monophosphate from a Water–Ethanol System

Metastable zone widths (MSZWs) and induction times (tind’s) were measured by turbidity techniques during the antisolvent crystallization of disodium guanosine 5′-monophosphate (5′-GMPNa2). Measured MSZWs can be affected by numerous process parameters, including temperature, the agitation rate, and the antisolvent addition rate. An exponential equation was used to correlate the supersolubility and solubility data for different conditions, and to afford predictions of the MSZW values. Values of tind at different temperatures and mole fractions of water were assessed to determine the primary nucleation and growth mechanisms of 5′-GMPNa2 crystals in the water–ethanol system. The measured tind’s were then correlated using mononuclear and polynuclear mechanistic models. The fitting results identified the primary nucleation mechanism for 5′-GMPNa2 as polynuclear, which relates tind and the supersaturation for various growth mechanisms. The growth mechanism of 5′-GMPNa2 was found to be diffusion-controlled at all experimental temperatures.

Supramolecular hydrogels derived from silver ion-mediated self-assembly of 5′-guanosine monophosphate

We describe the preparation and properties of supramolecular hydrogels produced by spontaneous self-association of disodium guanosine 5′-monophosphate (Na25′GMP) in the presence of Ag+ ions. Hydrogels with increasing viscosity are prepared by increasing the GMP:Ag stoichiometry from a molar ratio of 1 : 1 to 1 : 2. In each case, the hydrogels comprise an interconnected matrix of nanofilaments that undergo a gel to sol transition between 50–80 °C, depending on the matrix composition. NMR, UV-vis and CD spectroscopy investigations, in combination with XRD and SAXS studies indicate that the nanofilaments are constructed from helically stacked, chiral arrays of Ag-GMP dimers. Cationic dyes such as methylene blue and Hoechst-33258 bind to the Ag-GMP nanofilaments, with the latter dye exhibiting induced chirality transfer and significantly disrupting the hydrogel superstructure. Protein molecules (cytochrome c) can be immobilized within the hydrogels without loss of enzymatic activity. We also show that nanocomposite hydrogels comprising Ag-GMP nanofilaments impregnated with plasmonic Ag nanoparticles can be readily prepared by prolonged exposure to light.

Disodium Guanosine 5‘-Monophosphate Self-Associates into Nanoscale Cylinders at pH 8: A Combined Diffusion NMR Spectroscopy and Dynamic Light Scattering Study

We report a combined NMR and dynamic light scattering (DLS) study on the size of supramolecular structures formed by disodium guanosine 5'-monophosphate, Na(2)(5'-GMP), at pH 8. In general, two distinct types of aggregate species are present in an aqueous solution of Na(2)(5'-GMP). One type consists of stacking 5'-GMP monomers, and the other contains stacking G-quartets. Both types of aggregates can be modeled as rodlike cylinders. The cylinder diameter is 10 and 26 A for monomer aggregates and quartet aggregates, respectively. For Na(2)(5'-GMP) concentrations between 18 and 34 wt %, the cylinders formed by stacking G-quartets have an average length between 8 and 30 nm, corresponding to a stack of approximately 24-87 G-quartets. These nanoscale aggregates are significantly larger than what had previously been believed for Na(2)(5'-GMP) self-association at pH 8. The length of both types of 5'-GMP aggregates was found to increase with Na(2)(5'-GMP) concentration but was insensitive to the added NaCl in solution. While the aggregate size for monomer aggregates increases with a decrease in temperature, the size of G-quartet aggregates is essentially independent of temperature. We found that the size of G-quartet aggregates is slightly larger in D(2)O than in H(2)O, whereas the size of monomer aggregates remains the same in D(2)O and in H(2)O. We observed a linear relationship between the axial ratio of the 5'-GMP cylinders and the Na(2)(5'-GMP) concentration for both types of 5'-GMP aggregates, which suggests a common stacking mechanism for monomers and G-quartets.

Phosphorus-31 magnetization-transfer NMR studies of the interchange between structures of self-assembled disodium guanosine 5'-monophosphate in solution

Phosphorus-31 magnetization-transfer NMR studies of the interchange between structures of self-assembled disodium guanosine 5'-monophosphate in solution

NMR studies of self-association of disodium guanosine 5'-monophosphate

NMR studies of self-association of disodium guanosine 5'-monophosphate

Structure of disodium guanosine 5'-phosphate heptahydrate

Structure of disodium guanosine 5'-phosphate heptahydrate

Structure of disodium guanosine 5'-phosphate heptahydrate

Na2[CgHllN2OgP].7H20, M r = 494.0,orthorhombic, C222~, a = 22.880 (7), b = 8.877 (3),c = 19.592 (9) A, Z = 8, V = 3979.2 A 3. The Cu Ka intensity data consisted of 1005 unique reflections. Final R -- 14.5%. This nucleotide shows no unusual conformational features. The uracil base has an anti conformation about the glycosidic bond (tpo o = 44.4°). The furanose ring conformation is C(2')-endo,gauchegauche with tpo o = -75.5 ° and ~Poc = 496°.