Zhanzhong Wang

Crystallization control of thermal stability and morphology of hen egg white lysozyme crystals by ionic liquids.

Ionic liquids (ILs) exhibit a variety of properties that make them attractive additives for biomaterials. 1-Butyl-3-methylimidazolium tetrafluoroborate ([C(4)mim]BF(4)), 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl), 1-butyl-3-methylimidazolium bromide ([C(4)mim]Br), and 1,3-dimethylimidazolium iodine([bmim]I), as additives during lysozyme crystallization, were tested for their effects on the thermal stability and morphology of lysozyme crystals obtained. [C(4)mim]Cl was chosen to evaluate the effect of IL addition concentration on the thermal stability of lysozyme. It is shown that the characteristic peak temperature and endothermic enthalpy values (DeltaH) for denaturation increase with increasing addition concentration. As for the degradation, peak temperatures decrease, whereas endothermic enthalpy values markedly increase with the rise of [C(4)mim]Cl addition concentration. In the case of adding [C(4)mim]BF(4), [C(4)mim]Br, and [bmim]I, similar thermal behaviors of lysozyme crystals were observed. The effect of ILs on thermal behaviors of lysozyme can be attributed to enhancing crystal contacts, changing conformational stability, or interaction among molecules, as evidenced by difference in crystal growth morphology. This study is especially helpful in controlling the thermal stability of lysozyme crystals and in gaining initial insight into potential crystallization conditions for prescreening ILs that stabilize the protein and other macromolecule crystals.

Physicochemical properties and micro-structural characteristics in starch from kudzu root as affected by cross-linking

Kudzu starch was cross-linked with sodium trimetaphosphate (STMP) at different temperatures, time and of STMP concentrations in this work. The cross-linked starches (CLSs) were fractionated further into cross-linked amylose and amylopectin in order to compare the effect of cross-linking on the microstructure. According to scanning electron microscope (SEM), CLSs displayed the resemble appearance of spherical and polygonal shapes like NS. X-ray diffraction (XRD) revealed that amylose of native starch (A), NS and CLS displayed a combination of A-type and B-type structure, while that was not found in amylose of cross-linked starch (CLA). The deconvoluted fourier transform infrared (FT-IR) indicated that crystal structure of kudzu starch was losing with the proceeding of cross-linking reaction. The CLSs exhibited a higher retrogradation and freeze-thaw stability than NS. This was accompanied by a significant decrease in sedimentation, transparency, swelling power and solubility.

Preparation, crystal structure and solution-mediated phase transformation of a novel solid-state form of CL-20

Herein, the 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) acetonitrile solvate, a novel solid-state form of CL-20, was first discovered and characterized by various analytical techniques. The results of single-crystal X-ray diffraction (SCXRD) indicate that it is a channel-type solvate. Intermolecular interactions inside the crystal were investigated to elucidate the assembly behaviors with the assistance of the Hirshfeld surface analysis. The solvation profile and solubility data were determined to identify the thermodynamic stability of the acetonitrile solvate and form e. The solution-mediated phase transformation (SMPT) from the acetonitrile solvate to form e in acetonitrile–chloroform mixed solvents was online monitored by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and in situ Raman spectroscopy. The results reveal that the nucleation and growth of the form e is the rate-determining step. Moreover, the Johnson–Mehl–Avrami (JMA) model was employed to obtain deeper insights into the transformation kinetics. Furthermore, the effects of solvent composition, solid loading, and agitation rate were examined. This study provides an alternative approach for obtaining the desired form e crystals and lays a foundation for the optimization of the crystallization process in the future.

A new strategy for protein crystallization : Effect of ionic liquids on lysozyme crystallization and morphology

Protein crystallization is a complex physical and chemical process. The high-quality protein crystal is still a persistent bottleneck to the application of X-ray crystallography in structural biology. The additives may promote formation of crystal nucleus and subsequent growth in protein crystallization. As a distinct material, ionic liquids (ILs) have aroused great attention and interest for protein crystallization due to their unique properties. We reviewed the progress of protein crystallization and reported research about protein crystal morphology control by ILs, as crystal growth template, in aqueous solutions. ILs encourage changes in some cases in terms of growth morphology and crystal size. The effect of ILs on lysozyme growth morphology can be attributed to changing interaction among lysozyme molecules in aqueous solutions. This work can provide some initial insight into the preparation of high quality crystal and the development of new crystal form.

Novel Fluorescent Microemulsion: Probing Properties, Investigating Mechanism and Unveiling Potential Application

Nanoscale microemulsions have been utilized as delivery carriers for nutraceuticals and active biological drugs. Herein, we designed and synthesized a novel oil in water (O/W) fluorescent microemulsion based on isoamyl acetate, polyoxyethylene castor oil EL (CrEL), and water. The microemulsion emitted bright blue fluorescence, thus exhibiting its potential for active drug detection with label-free strategy. The microemulsion exhibited excitation-dependent emission and distinct red shift with longer excitation wavelengths. Lifetime and quantum yield of fluorescent microemulsion were 2.831 ns and 5.0%, respectively. An excellent fluorescent stability of the microemulsion was confirmed by altering pH, ionic strength, temperature, and time. Moreover, we proposed a probable mechanism of fluorochromic phenomenon, in connection with the aromatic ring structure of polyoxyethylene ether substituent in CrEL. Based on our findings, we concluded that this new fluorescent microemulsion is a promising drug carrier that can facilitate active drug detection with a label-free strategy. Although further research is required to understand the exact mechanism behind its fluorescence property, this work provided valuable guidance to develop new biosensors based on fluorescent microemulsion.

Effects of inorganic additives on polymorphs of glycine in microdroplets

Salt-dependent polymorphic control of glycine was investigated by using the microdroplet technique in this work. Sodium chloride (NaCl) was chosen as the additive to probe the influence of inorganic ions on the polymorphic nucleation of glycine. The thermodynamics and nucleation kinetics of glycine polymorphs in microdroplets were systematically analyzed based on the microdroplet technique. The crystal structures of the polymorphs were confirmed by powder X-ray diffraction (PXRD). The results illustrate that the critical concentration of NaCl required to induce the pure γ-form in the microdroplets is lower than that in the conventional method, which means that the microdroplet technique is more sensitive for the control of polymorph nucleation. The polymorphic nucleation selectivity of glycine was then discussed in view of classical nucleation theory. The results demonstrate that NaCl reduces the nucleation energy barrier of the γ-form of glycine, and for the same form of glycine, crystallization by the conventional method has a higher interfacial tension than in microdroplets.

Manipulating crystallization in lysozyme and supramolecular self-arrangement in solution using ionic liquids

Manipulating crystallization for macromolecule using ionic liquids (ILs) as an additive has received great attention, but how ILs accurately control their formation and crystallization pathway remains unclear. Here, we aim to illuminate the role of ILs on the solution chemistry of macromolecules by investigating their effects on the crystallization of lysozyme. The solubility findings show ILs changed intermolecular contacts, leading to lysozyme supramolecular repulsive interactions being induced or attractive interactions enhanced. Lysozyme was crystallized in the form of tetragonal crystals in the presence of [C4mim]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate), [C4mim]Cl (1-butyl-3-methylimidazolium chloride) and [C4mim]Br (1-butyl-3-methylimidazolium bromide), while it was crystallized in the form of monoclinic crystals in the presence of [dmim]I (1,3-dimethylimidazolium iodine). Compared with that in the absence of ILs, lysozyme in the presence of [C4mim]Cl and [dmim]I contained a decreased α-helix content, but increased β-sheet content. The presence of [dmim]I also caused the β-turn content to increase and random coil content to decrease. This demonstration shows the formation of crystal nucleus is involved in transition at the protein secondary structure level, which may contribute to a better understanding of the role of ILs in the crystallization of bio-macromolecular materials and to developing a strategy to produce new bio-macromolecular materials using ILs.

The Controllable Preparation, Properties and Structural Characteristics of Xylitol/Menthol Co-crystals

Abstract Xylitol is fast gaining ground over other sugar substitute owing to its high sweeting and low calorie properties. Menthol, a flavor agent, is widely used in food production. However, menthol can easily sublimate, while xylitol has a strong hygroscopicity. In this study, the co-crystals of xylitol with menthol are performed aiming to improve their negative properties. The results indicated that the water activity of co-crystals varies from 0.126 to 0.370. Meanwhile, the hygroscopicity of co-crystals is reduced to some extent compared with xylitol. Differential scanning calorimetry results demonstrated that co-crystals have similar thermal properties. What’s more, co-crystals have nearly identical X-ray diffraction patterns with xylitol. Thus, it is suggested that the microstructure of co-crystals is influenced mostly by the compound with a high ratio. Overall, this study can convey important idea for the development of food new materials, also the control and application based on co-crystallization techniques in food industry.

Solvated behavior and crystal growth mechanism of erythromycin in aqueous acetone solution

The solubility of erythromycin acetone solvate and dihydrate was experimentally determined in aqueous acetone mixtures at different temperature. It has been demonstrated that solubility curves of the two solvates intersected at given solvent composition at various temperature, suggesting a transition behavior between two solvates. The induction period of acetone solvate at different supersaturation was measured by the laser monitoring observation technique. Based on classical homogeneous nucleation theory, the solid-liquid interfacial tension and surface entropy factor were calculated from the induction period data. From the surface entropy factor values calculated, together with surface morphology observation by the atomic force microscopy (AFM), the growth mechanism of erythromycin acetone solvate is consistent with continuous growth mode.