Denaturing Effects of Urea and Guanidine Hydrochloride on Hyperthermophilic Esterase from Aeropyrum pernix K1

The changes in the activity and the conformation of the hyperthermophilic esterase derived from aerobic thermophilic Aeropyrum pernix K1 （ APE1547 ） were studied during denaturation by guanidine hydrochlofide （ GdnHC1 ） and urea. The denaturation course of APE1547 was followed by the steady-state and time resolved fluorescence methods. An increase in the denaturant concentration in the denatured system can significantly enhance the inactivation and unfolding of APE1547. The enzyme can be completely inactivated with a urea concentration of 2.7 mol/L or a GdnHCl concentration of 7.5 mol/L. The fluorescence emission maximum of the enzyme protein red shifts in magnitude to a maximum value（355 nm） when the concentration of GdnHCl is 5.1 mol/L. The experimental results indicate that APE1547 has a high resistance to urea. Unfolding of APE1547 in GdnHCI（4. 2-6.0 mol/L） was shown to be an irreversible process. The present results indicate that the ion pairs in this protein may be a key factor for the stability of this esterase.

New Approach to Synthesis of Silica with Chemically Bound Guanidine Hydrochloride for Preconcentration of Metal Ions

Guanidine hydrochloride was chemically bonded to surface of modified silica by means of condensation with grafted amino groups. Ion-exchanging and complexing properties of the obtained adsorbent have been studied with respect to cations of Zn(II), Cu(II), Pb(II), Cd(II), Co(II) and metal-containing oxoanions of W(VI), Mo(VI), Cr(VI), V(V). Optimum conditions for quantitative extraction of the studied ions were determined. The structure and composition of Co(II) and Cu(II) complexes on the surface of the synthesized adsorbent have been investigated. The possibility of quantitative determination of cobalt(II) and copper(II) trace amounts after their preconcentration by the synthesized adsorbent was demonstrated.

A novel kind of TSV slurry with guanidine hydrochloride

The effect of a novel alkaline TSV （through-silicon-via） slurry with guanidine hydrochloride （GH） on CMP （chemical mechanical polishing） was investigated. The novel alkaline TSV slurry was free of any inhibitors. During the polishing process, the guanidine hydrochloride serves as an effective surface-complexing agent for TSV CMP applications, the removal rate of barrier （Ti） can be chemically controlled through tuned selectivity with respect to the removal rate of copper and dielectric, which is helpful to modifying the dishing and gaining an excellent topography performance in TSV manufacturing. In this paper, we mainly studied the working mechanism of the components of slurry and the skillful application guanidine hydrochloride in the TSV slurry.

Unfolding of C2A Domain of Synaptotagmin I in the Presence of Guanidine Hydrochloride

The C2 domain originally referred to the second of four constant structural motifs in protein kinase C (PKC). Now this domain represents a large structural family sharing a homologous dimensional structure in many proteins that play important roles in many organisms. The C2A domain is one of the two C2 domains of synaptotagmin I involved in the Ca 2+ regulation of exocytosis. This domain is mostly composed of β sheet except for a small fraction of α helix, and therefore provides an ideal model for a protein folding study. In this report, the unfolding equilibrium of the C2A domain in guanidine hydrochloride (GdnHCl) containing solutions has been studied using ultraviolet (UV) difference spectrum, fluorescence spectrum, size exclusion chromatography (SEC), and circular dichroism (CD) spectrum. The results suggest that unfolding of the C2A domain occurs as a two state process during GdnHCl titration. By examining the changes of both tertiary structure and secondary structure, no intermediates could be detected during this unfolding study. However, it has been found that the native state of the C2A domain has a large hydrophobic surface. This result suggests that as a fragment of a protein, the C2A domain itself may exist in a state with large hydrophobic surface. This hydrophobic surface may be the molecular basis for interaction between domains in the whole protein. Furthermore, the hydrophobic behavior may play a role during the oligomerization of synaptotagmin.

Effect of guanidine hydrochloride on removal rate selectivity and wafer topography modification in barrier CMP

We propose an alkaline barrier slurry containing guanidine hydrochloride（GH） and hydrogen peroxide.The slurry does not contain any corrosion inhibitors, such as benzotriazole（BTA）. 3-inch samples of tantalum copper and oxide were polished to observe the removal rate. The effect of GH on removal rate selectivity along withhydrogenperoxidewasinvestigatedbycomparingslurrycontainingGHandH2O2withslurrycontainingonly GH. Details about the tantalum polishing mechanism in an alkaline guanidine-based slurry and the electrochemical reactions are discussed. The results show that guanidine hydrochloride can increase the tantalum polishing rate and the selectivity of copper and barrier materials. The variation of the dishing and wire line resistance with the polishing time was measured. The dishing value after a 300 mm pattern wafer polishing suggests that the slurry has an effective performance in topography modification. The result obtained from the copper wire line resistance test reveals that the wire line in the trench has a low copper loss.

Preparation of guanidine-modified starch for antimicrobial paper

Normal paper does not have antimicrobial properties.To impart antimicrobial properties to paper for medical applications,a guanidine-modified starch was prepared via two reaction steps using guanidine hydrochloride(GH)as a modifier,and added to the paper coating formula.FT-IR demonstrated that the GH was successfully grafted onto the starch via the Schiff base reaction.After coating with the modified starch,the antimicrobial performance of the paper against E.coli and S.aureus was evaluated by the disc diffusion method.The results indicated that the paper treated with the guanidine-modified starch exhibited excellent antimicrobial properties against the E.coli and S.aureus.In addition,the dry and wet strength indexes of the coated paper increased by 25%and 100%,respectively,as compared to the control paper.

Spectral Studies on the Conformational Transitions of Bovine Insulin During Denaturant-induced Unfolding

Transitions among various molecule states and conformational changes of bovine insulin were investigated under different denaturing conditions by means of fluorescence phase diagrams,fluorescence quenching,1-anilinonaphthalene-8-sulfonate（ANS） binding assay and circular dichroism（CD） spectra.In both guanidine hydrochloride（GuHCl）-and urea-denatured procedures,the spatial structure of insulin molecules changed from ordered states to relative unordered ones with the increasing of denaturant concentration.The GuHCl-denatured process followed a four-state model,for there were two intermediates existed in 2.0 and 6.0 mol/L GuHC1,respectively.Intermediate I1 is more compact than the normal protein.And intermediate I2 has lost most of the secondary structures.When GuHCl concentration was above 6.0 mol/L,the fluorophores originally existed in the internal of insulin molecules would expose to the surface.However,the urea-denatured process followed a three-state model,only one intermediate existed in 2.5 mol/L urea.During the urea-denatured procedure,the fluorophores originally existed in theinternal of insulin molecules didn＇t expose to the surface.

Effect of Denaturant Concentration on Hen-egg White Lysozyme Renaturation

Based on three-state renaturation process of denatured proteins, an equation describing the effect of denaturant concentration on renaturation yield of denatured proteins was presented. By this equation, two parameters n（m1 -m2） and Ka can be obtained. The former indicates the difference in the number of denaturant molecules between the renaturation process of n number of refolding intermediates from refolding intermediate state to native state and their aggregate process from refolding intermediate state to aggregate state, the latter denotes the apparent aggregate equilibrium constant for protein molecules aggregated from native state to aggregate state, and from them, the characteristics of the renaturation process of denatured proteins in denaturant solution can be identified. This equation was tested by the renaturation processes of denatured egg white lysozyme in guanidine hydrochloride and urea solutions, with the results to show that when guanidine hydrochloride and urea concentrations were separately higher than 1.25 and 3.00 mol/L or separately lower than 1.00 and 3.00 mol/L, the refolding intermediates of egg white lysozymes were more easily aggregated to aggregate state or more easily renatured to native state, respectively. Under different initial total egg white lysozyme concentrations in urea solution, the refolding egg white lysozyme intermediates could be deduced to have a tendency to form a bimolecular intermediate aggregate, and this inference was further confirmed by their nonreducing SDS-PAGE and size exclusion chromatography.

Contributions of a Position Amino Acid Residues to the Conformational Stability of GCN4 Leucine Zipper

The stability of GCN4 leucine zipper and its four mutants in guanidine hydrochloride was detected to verify the contributions of different a position amino acid residues in polypeptide sequences to the forming and stability of parallel coiled coils. The changes of the circular dichroism spectra show that the displace- ment of the a position polar asparagine and the increase of asparagine in the GCN4 leucine zipper can reduce the α-helix content of the coiled coil structure. The mutants are less stable than the natural peptide in guanidine hydrochloride. The results show that the interaction between the polar asparagine contributes to the conformational stability of the coiled coil. Both the conformation and the number of polar residues in the coiled coil also affect the α-helix content and its resistance to the denaturant. The conclusions provide evidence describing the folding process of proteins including coiled coils in vivo.