Role of resistin in the inflammatory response induced by nicotine plus lipopolysaccharide in human periodontal ligament cells in vitro

BACKGROUND AND OBJECTIVE

Resistin was recently reported to play a role in inflammation-related diseases such as arthritis. However, the precise role of resistin in chronic inflammatory diseases, such as periodontal disease, remains unclear. The aim of this study was to investigate the combined effects of nicotine and lipopolysaccharide (LPS) on the expression of resistin and to assess whether resistin expression influences the levels of inflammatory cytokines, extracellular matrix (ECM) molecules and MMPs in human periodontal ligament cells (PDLCs) stimulated with both nicotine and LPS.

MATERIAL AND METHODS

PDLCs were pretreated with isoproterenol or resistin-specific small interfering RNA (siRNA), stimulated with LPS plus nicotine for 24 h, and then monitored for the production of inflammatory mediators. The concentrations of prostaglandin E2 (PGE2) and nitric oxide (NO) were measured by radioimmunoassay and the Griess method, respectively. RT-PCR and western blot analysis were used to measure the levels of mRNA and protein, respectively. Western blot analysis was also used to assess the activation of various signal-transduction pathways.

RESULTS

Treatment with nicotine plus LPS up-regulated the expression of resistin mRNA and the production of resistin protein in PDLCs in a time- and concentration-dependent manner. Isoproterenol-mediated interference with the function of resistin, or siRNA-mediated knockdown of resistin expression, markedly attenuated the LPS plus nicotine-mediated stimulation of PGE2 and NO production, the production of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase proteins and the expression of proinflammatory cytokines [tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-12] and MMPs (MMP-1, MMP-2 and MMP-9); however, these treatments restored the expression of ECM molecules. Furthermore, pretreatment with isoproterenol or resistin-specific siRNA blocked nicotine plus LPS-induced activation of phosphoinositide-3-kinase, glycogen synthase kinase-3 beta, β-catenin, p38, ERK, JNK and nuclear factor-κB.

CONCLUSION

This is the first study to show that the inhibition of resistin, by either a pharmacological or a genetic silencing approach, has anti-inflammatory effects. These effects include decreased levels of inflammatory cytokines and the prevention of ECM breakdown in a nicotine plus LPS-stimulated PDLC model.

The role of external defects in chemical sensing of graphene field-effect transistors

A fundamental understanding of chemical sensing mechanisms in graphene-based chemical field-effect transistors (chemFETs) is essential for the development of next generation chemical sensors. Here we explore the hidden sensing modalities responsible for tailoring the gas detection ability of pristine graphene sensors by exposing graphene chemFETs to electron donor and acceptor trace gas vapors. We uncover that the sensitivity (in terms of modulation in electrical conductivity) of pristine graphene chemFETs is not necessarily intrinsic to graphene, but rather it is facilitated by external defects in the insulating substrate, which can modulate the electronic properties of graphene. We disclose a mixing effect caused by partial overlap of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of adsorbed gas molecules to explain graphene's ability to detect adsorbed molecules. Our results open a new design space, suggesting that control of external defects in supporting substrates can lead to tunable graphene chemical sensors, which could be developed without compromising the intrinsic electrical and structural properties of graphene.

Effect of SNPs on creatine kinase structure and function: identifying potential molecular mechanisms for possible creatine kinase deficiency diseases

Single-nucleotide polymorphisms (SNPs) are common genetic material changes that often occur naturally. SNPs can cause amino acid replacements that may lead to severe diseases, such as the well-known sickle-cell anemia. We constructed eight SNP mutants of human brain-type creatine kinase (CKB) based on bioinformatics predictions. The biochemical and biophysical characteristics of these SNP mutants were determined and compared to those of the wild-type creatine kinase to explore the potential molecular mechanisms of possible creatine kinase SNP-induced diseases. While the reactivation of six SNP mutants after heat shock dropped more than 45%, only three of them showed notable increases in ANS fluorescence intensity and decreases in catalytic efficiency. Among them, H26Y and P36T bind substrates as well as the wild-type form does, but the melting temperatures (T_m) dropped below body temperature, while the T59I mutant exhibited decreased catalytic activity that was most likely due to the much reduced binding affinity of this mutant for substrates. These findings indicate that SNPs such as H26Y, P36T and T59I have the potential to induce genetic diseases by different mechanisms.

The effect of fucoidan on tyrosinase: computational molecular dynamics integrating inhibition kinetics

Fucoidan is a complex sulfated polysaccharide extracted from brown seaweed and has a wide variety of biological activities. In this study, we investigated the inhibitory effect of fucoidan on tyrosinase via a combination of inhibition kinetics and computational simulations. Fucoidan reversibly inhibited tyrosinase in a mixed-type manner. Time-interval kinetics showed that the inhibition was processed as first order with biphasic processes. For further insight, we simulated dockings with various sizes of molecular models (monomer to decamer) of fucoidan and showed that the best binding energy change results were obtained from the pentamer (-1.89 kcal/mol) and the hexamer (-1.97 kcal/mol) models of AutoDock Vina. The molecular dynamics simulation confirmed the binding mechanisms between tyrosinase and fucoidan and suggested that fucoidan mostly interacts with several residues including copper ions located in the active site. Our study suggests that fucoidan might be a potential natural antipigment agent.

Sodium alginate hydrogel-based bioprinting using a novel multinozzle bioprinting system

Bioprinting is a technology for constructing bioartificial tissue or organs of complex three-dimensional (3-D) structure with high-precision spatial shape forming ability in larger scale than conventional tissue engineering methods and simultaneous multiple components composition ability. It utilizes computer-controlled 3-D printer mechanism or solid free-form fabrication technologies. In this study, sodium alginate hydrogel that can be utilized for large-dimension tissue fabrication with its fast gelation property was studied regarding material-specific printing technique and printing parameters using a multinozzle bioprinting system developed by the authors. A sodium alginate solution was prepared with a concentration of 1% (wt/vol), and 1% CaCl(2) solution was used as cross-linker for the gelation. The two materials were loaded in each of two nozzles in the multinozzle bioprinting system that has a total of four nozzles of which the injection speed can be independently controlled. A 3-D alginate structure was fabricated through layer-by-layer printing. Each layer was formed through two phases of printing, the first phase with the sodium alginate solution and the second phase with the calcium chloride solution, in identical printing pattern and speed condition. The target patterns were lattice shaped with 2-mm spacing and two different line widths. The nozzle moving speed was 6.67 mm/s, and the injection head speed was 10 µm/s. For the two different line widths, two injection needles with inner diameters of 260 and 410 µm were used. The number of layers accumulated was five in this experiment. By varying the nozzle moving speed and the injection speed, various pattern widths could be achieved. The feasibility of sodium alginate hydrogel free-form formation by alternate printing of alginate solution and sodium chloride solution was confirmed in the developed multinozzle bioprinting system.

Trifluoroethanol-induced changes in activity and conformation of manganese-containing superoxide dismutase

Superoxide dismutase (SOD, EC 1.15.1.1) plays an important role in antioxidant defense in organisms exposed to oxygen. However, there is a lack of research into the regulation of SOD activity and structural changes during folding, especially for SOD originating from extremophiles. We studied the inhibitory effects of trifluoroethanol (TFE) on the activity and conformation of manganese-containing SOD (Mn-SOD) from Thermus thermophilus. TFE decreased the degree of secondary structure of Mn-SOD, which directly resulted in enzyme inactivation and disrupted the tertiary structure of Mn-SOD. The kinetic studies showed that TFE-induced inactivation of Mn-SOD is a first-order reaction and that the regional Mn-contained active site is very stable compared to the overall structure. We further simulated the docking between Mn-SOD and TFE (binding energy for Dock 6.3, -9.68 kcal/mol) and predicted that the LEU9, TYR13, and HIS29 residues outside of the active site interact with TFE. Our results provide insight into the inactivation of Mn-SOD during unfolding in the presence of TFE and allow us to describe ligand binding via inhibition kinetics combined with computational predictions.

Effects of acrylamide on the activity and structure of human brain creatine kinase

Acrylamide is widely used worldwide in industry and it can also be produced by the cooking and processing of foods. It is harmful to human beings, and human brain CK (HBCK) has been proposed to be one of the important targets of acrylamide. In this research, we studied the effects of acrylamide on HBCK activity, structure and the potential binding sites. Compared to CKs from rabbit, HBCK was fully inactivated at several-fold lower concentrations of acrylamide, and exhibited distinct properties upon acrylamide-induced inactivation and structural changes. The binding sites of acrylamide were located at the cleft between the N- and C-terminal domains of CK, and Glu232 was one of the key binding residues. The effects of acrylamide on CK were proposed to be isoenzyme- and species-specific, and the underlying molecular mechanisms were discussed.

Where has the tumor gone? The characteristics of cases of negative pathologic diagnosis after endoscopic mucosal resection

BACKGROUND AND STUDY AIMS

Discrepancies can occur between the histopathological findings from forceps biopsy and endoscopic mucosal resection (EMR), and occasionally in embarrassing cases tumorous tissue is not found at EMR. The aim of the present study was to evaluate the clinical, endoscopic, and histological features of gastric tumors in patients with pathololgically negative findings at EMR.

PATIENTS AND METHODS

We retrospectively reviewed data from all patients with gastric tumor treated with EMR or endoscopic submucosal dissection (ESD) between August 1999 and April 2007 at our institution, and enrolled into the study patients with no tumor tissue found at mucosal resection. Their biopsy and EMR specimen slides were reviewed by a single pathologist. Patient characteristics, including demographic and clinical features, and the endoscopic appearance of mucosal lesions were evaluated.

RESULTS

Out of 633 patients treated with EMR or ESD, 20 patients (3.2 %) were included. The mean +/- SD maximal dimension of the mucosal lesions was 6.40 +/- 2.19 mm (range 3 - 10). Mean number of forceps biopsy fragments was 3.80 +/- 1.96 and mean sampling ratio was 2.08 +/- 1.07 mm/fragment. Before resection, histological findings from forceps biopsy were: 13 low grade dysplasias (65.0 %), 2 high grade dysplasias (10.0 %), and 5 intramucosal carcinomas (25.0 %).

CONCLUSIONS

In the case of pathologically negative findings at EMR, tumors might have been small enough to have been removed by the previous forceps biopsy. However, the possibility of sampling error or of a different location should be considered. Furthermore, appropriate communication between endoscopists and pathologists is essential.

Histone deacetylase inhibitor scriptaid induces cell cycle arrest and epigenetic change in colon cancer cells

Histone deacetylase inhibitors (HDACIs) are involved in cell growth, apoptosis and differentiation. This study aimed to investigate the effects of HDACI scriptaid on histone modification, demethylation, cell growth, cell cycle and apoptosis in the RKO colorectal cancer cell line and screening for scriptaid-induced genes. RKO cells were treated with 5-aza-2'-deoxycytidine (5-aza-dC), trichostatin A (TSA) or scriptaid at different concentrations. Histone modification and methylation status of a silenced p16 gene were analyzed using chromatin immunoprecipitation and methylation-specific PCR, respectively. Flow cytometry was performed for the analysis of cell cycle and apoptosis. Scriptaid-induced expression was analyzed using Human OneArray chip. Scriptaid resulted in the demethylation and re-expression of a hypermethylated p16 gene along with 5-aza-dC synergistically in the RKO cells, but not alone. Scriptaid induced modifications of core histone tails important in euchromatin structure: increases in acetyl-H3-K9 and dimethyl-H3-K4 and a decrease in dimethyl-H3-K9. Cell growth was inhibited by scriptaid in a dose-dependent manner. Cell cycle analysis showed that scriptaid induced G1 arrest at 0.5 and 1.0 microM concentrations and G1 and G2/M arrest at 2.0 microM. Scriptaid did not have a significant effect on apoptosis in RKO cells. An altered expression of 278 genes was observed in RKO cells in response to scriptaid treatment. In conclusion, the present study suggests that scriptaid may be effective in growth suppression and cell cycle arrest and in the reversal of repressive chromatin marks at the promoter region of a hypermethylated p16 gene in colorectal cancer.

A cell culturing system that integrates the cell loading function on a single platform and evaluation of the pulsatile pumping effect on cells

In this paper, we present a novel microfluidic system with pulsatile cell storing, cell-delivering and cell culturing functions on a single PDMS platform. For this purpose, we have integrated two reservoirs, a pulsatile pumping system containing two soft check valves, which were fabricated by in situ photopolymerization, six switch valves, and three cell culture chambers all developed through a simple and rapid fabrication process. The sample volume delivered per stroke was 120 nl and the transported volume was linearly related to the pumping frequency. We have investigated the effect of the pulsatile pneumatic micropumping on the cells during transport. For this purpose, we pumped two types of cell suspensions, one containing human breast adenocarcinoma cells (MCF-7) and the other mesenchymal stem cells (hMSCs) derived from bone marrow. The effect of pulsatile pumping on both cell types was examined by short and long-term culture experiments. Our results showed that the characteristics of both cells were maintained; they were not damaged by the pumping system. Evaluations were carried out by morphological inspection, viability assay and immunophenotyping analysis. The delivered MCF-7 cells and hMSCs spread and proliferated onto the gelatin coated cell culture chamber. This total micro cell culture system can be applied to cell-based high throughput screening and for co-culture of different cells with different volume.

Factors related to lymph node metastasis and the feasibility of endoscopic mucosal resection for treating poorly differentiated adenocarcinoma of the stomach

BACKGROUND AND AIM

Endoscopic mucosal resection (EMR) is currently not accepted as an alternative treatment to surgery in early gastric cancer (EGC) of the undifferentiated histologic type. The present retrospective analysis examined the correlation of various histologic factors with the presence of lymph node metastasis (LNM).

PATIENTS AND METHODS

A retrospective analysis on 234 patients with poorly differentiated EGC who underwent radical gastrectomy with D2 lymph node dissection was undertaken. Several clinicopathologic factors were investigated to identify predictive factors for LNM: age, sex, type of operation, tumor location, tumor size, gross type, ulceration, lymphatic invasion, and depth of invasion.

RESULTS

Of the 234 lesions with poorly differentiated EGC, half (n = 116) already showed submucosal invasion in the resection specimen; 25.9 % of those (30/116) were limited to the upper third (SM1). Of the lesions confined to the mucosa, LNM was found in 3.4 % (4/118). With minor submucosal infiltration (SM1), the LNM rate was lower (0/30) in our patient population. Only with SM2/3 infiltration did the LNM rate sharply rise to around 30 %. The cut-off for submucosal infiltration depth was 500 microm (0/32 LNM), above which LNM rates were substantial (31.2 %; 24/77). There was limited correlation between the SM1-3 classification and actual measurement of submucosal infiltration depth. In a multivariate analysis, tumor size ( P = 0.033), depth of invasion ( P = 0.004), and lymphatic invasion ( P < 0.001) were associated with LNM.

CONCLUSION

Poorly differentiated EGC confined to the mucosa or with minimal submucosal infiltration (<or= 500 microm) could be considered for curative EMR due to the low risk of LNM. Given the limited case number of subgroups, these findings should be confirmed by more data from other centers, which should also focus on local recurrence after EMR in poorly differentiated EGC.

Effect of Cl- on tyrosinase: complex inhibition kinetics and biochemical implication

Tyrosinase plays a core role in melanogenesis of the various organisms. Therefore, the regulation of the tyrosinase activity is directly related with melanin synthesis. In this study, we investigated the Cl(-)-induced inhibition of human tyrosinase and the potent role of Cl(-) as a negative regulator in melanogenesis. For the inhibition kinetic studies, human tyrosinase was differently prepared from the TXM13 melanotic cells as well as from cells that had undergone gene transfection. We found that Cl(-) inhibited tyrosinase in a slope-parabolic competitive manner and tyrosinase gene transfection into HEK293 cell significantly down-regulated the expression levels of solute carrier family 12, member 4 (potassium/chloride transporters, SLC12A7) and solute carrier family 12, member 7 (potassium/chloride transporters, SLC12A7), which are known to be Cl(-) transporters. From the results of the inhibition kinetic studies and the Cl(-) transporter expression level, we suggested that Cl(-) might act as a potent regulatory factor in melanogenesis. It is worth notice that a high content of Cl(-) exists physiologically and tyrosinase reacts sensitively to Cl- in a complex interaction manner.

Towards creatine kinase aggregation due to the cysteine modification at the flexible active site and refolding pathway

The dimeric native state of creatine kinase (CK) was aggregated at conspicuous levels during cysteine modification at the active site with using 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) under a high enzyme concentration. Measuring the ANS-binding fluorescence revealed that the hydrophobic surface of CK was increased by cysteine modification due to the flexible active site, and this resulted in insoluble aggregation, probably via non-specific hydrophobic interactions. To determine whether the aggregates can be refolded, 3M guanidine hydrochloride (GdnHCl) was used to dissolve the aggregates into the denatured form. Refolding of the solubilized enzyme sample was then conducted, accompanied by deprivation of DTNB from the CK in the presence of DTT. As a result, CK was reactivated by up to 40% with partial recovery of the tertiary (78%) and secondary structures (77%). To further elucidate its kinetic refolding pathway, both time interval measurements and a continuous substrate reaction were performed. The results showed that the refolding behavior was similar to the manner of normal CK folding with respect to the following two-phase kinetic courses. Additionally, the rate constants for the dimerization of the unfolded CK were dependent on the enzyme concentration and this was irrespective to the DTT concentrations, suggesting the rate-limiting steps of CK reassociation. The present study will expand our insight into the flexibility of the enzyme active site, which might act as a risk factor for inducing the unfavorable aggregation and partial refolding pathway of CK, as well as inducing an intermediate-like state recovery from aggregation.

"On the fly" continuous generation of alginate fibers using a microfluidic device

In this paper, we introduce a new continuous production technique of calcium alginate fibers with a microfluidic platform similar to a spider in nature. We have used a poly(dimethylsiloxane) (PDMS) microfluidic device embedded capillary glass pipet as the apparatus for fiber generation. As a sample flow, we introduced a sodium alginate solution, and, as a sheath flow, a CaCl2 solution was introduced. The coaxial flows were generated at the intersection of both flows, and the sodium alginate was solidified to calcium alginate by diffusion of the Ca2+ ions during traveling through the outlet pipet. The diameter changes in the sample and sheath flow variations were examined, and the size of alginate fibers was well regulated by changing both flow rates. In addition, we have measured the elasticity of dried fibers. We evaluated the potential use of alginate fibers as a cell carrier by loading human fibroblasts during the "on the fly" fabrication process. From the LIVE/DEAD assay, cells survived well during the fiber fabrication process. In addition, we evaluate the capability of loading the therapeutic materials onto the alginate fibers by immobilized bovine serum albumin-fluorescein isothiocyanate in the fibers.

Two-dimensional electrophoresis analyses of atopic dermatitis and the chances to detect new candidate proteins by the variations in immobilized pH gradient strips

BACKGROUND

Proteomic approaches, one of the high-throughput technologies, have been used to search for the proteins that are abnormally expressed in human diseases. The atopic dermatitis (AD)-associated genes or proteins are gradually being reported.

OBJECTIVE

In accordance with recent reports, we conducted the serial proteomic studies to compare with the protein expression level and to find a critical protein associated with AD.

METHODS

We applied two-dimensional electrophoresis (2-DE) coupled with MADI-TOF as well as LC-MS/MS to detect dysregulated protein in the AD proteome obtained from the patient-derived primary cells. Real-time PCR was also conducted to compare with the proteomic results in the transcriptional level.

RESULTS

We successfully detected new AD-associated proteins in the AD-derived fibroblasts 2D-PAGE studies due to the IPG strip variations after conducting MALDI-TOF mass spectrometry and identification of the proteins. From the real-time PCR quantifications, we found that the altered expression of caldesmon 1 isoform 5, nucleophosmin 1, esterase D and chloride intracellular channel 4 were well matched both at the transcriptional and translational levels, and this suggested that these proteins may have important involvement with the pathogenesis of AD.

CONCLUSION

By simply repeating the trials with changing the commercial strips with different lot numbers in the 2D-PAGE analysis, this provided us with new finding in the AD-derived samples. This approach we used may increase the chances of finding new candidate proteins in the clinical samples and it may also be applicable for proteomic studies of other diseases.

The inhibition kinetics and thermodynamic changes of tyrosinase via the zinc ion

We found that Zn(2+) conspicuously inactivated tyrosinase in a mixed-type inhibition manner: the final level of residual activity was abolished at the equilibrium state with concentration of 0.25 mM Zn(2+). Changes of both K(m) and V(max) by various concentrations of Zn(2+) in Lineweaver-Burk plot were observed. To see whether Zn(2+) also induced conformational change of tyrosinase and how thermodynamical changes by ligand binding were occurred, the intrinsic fluorescence studies as well as calorimetric measurements were conducted. The results showed that the Zn(2+) binding to tyrosinase directly induced conformational change of tyrosinase, and the changes of thermodynamic parameters such as enthalpy (DeltaH), Gibbs free-energy (DeltaG), and entropy (DeltaS) were obtained as 60+/-7.0 kJ/mol, -14.54 kJ/mol and 248.53 J/(K mol), respectively. The inactivating effect of Zn(2+) on tyrosinase was completely prevented by incubation with bovine serum albumin, which has a Zn(2+) binding motif in its structure. We suggested that Zn(2+) ligand-binding affected the substrate's accessibility due to the conformational changes and thus, the complex type of inhibition has occurred with the calorimetric changes.

Detection of down-regulated acetaldehyde dehydrogenase 1 in atopic dermatitis patients by two-dimensional electrophoresis

We conducted the proteomic studies to detect the dysregulated proteins in the atopic dermatitis (AD) proteome obtained from the patient-derived primary cultured fibroblasts. Acetaldehyde dehydrogenase 1 (ALDH1) was detected as being significantly down-regulated at the pH ranges of 6-9 and 4-7. The transcriptional levels of ALDH1, as detected by RT-PCR and real-time PCR, further confirmed the down-regulated phenomena for all the AD-fibroblasts (n = 20). The expression levels of ALDH1 in the whole skin tissue samples were further supported by the results of the primary cultured samples. These findings clearly demonstrate that ALDH1 can be a dermal biomarker for AD disease.

The protective effects of osmolytes on arginine kinase unfolding and aggregation

Osmolytes are a series of different kinds of small molecules that can maintain the correct conformation of protein by acting as molecular chaperons. In this study, the protective effects of four compatible osmolytes, i.e., proline, sucrose, DMSO and glycerol, were studied during arginine kinase (EC 2.7.3.3) unfolding and aggregation. The results showed that all the osmolytes applied in this study obviously prevented AK unfolding and inactivation that was due to a GdnHCl denaturant by reducing the inactivation rate constants (k(i)), increasing the transition free energy changes (DeltaDeltaG(i)) and increasing the value for the midpoint of denaturation (C(m)). Furthermore, the osmolytes remarkably prevented AK aggregation in a concentration-dependent manner during AK refolding. Our results strongly indicated that osmolytes were not only metabolism substrates, but they were also important compounds with significant physiological protective functions for proteins, especially in some extremely harsh environments.

Post-annealing effect on the electronic structure of Mn atoms in Ga(₁-x)Mn(x)As probed by resonant inelastic x-ray scattering

The electronic structure of as-grown and post-annealed Ga(₁-x)Mn(x)As epilayers (x≈0.055) has been investigated using resonant inelastic x-ray scattering. Mn L₂,₃ x-ray emission spectra show that the integral intensity ratio of Mn L₂ to L₃ emission lines increases with annealing temperature and comes close to that of manganese oxide. The oxygen K-emission/absorption spectra of post-annealed Ga₀.₉₄₅Mn₀.₀₅₅As show 1.5-3.0 times higher degree of oxidation on the film surface than that of the as-grown sample. These experimental findings are attributed to the diffusion of Mn impurity atoms from interstitial positions in the GaAs host lattice to the surface where they are passivated by oxygen.

Monomeric Creatine Kinase Aggregation and Sodium Dodecyl Sulfate-cyclodextrin Assisted Refolding

The monomeric state of creatine kinase (CK) was stably captured at the equilibrium state by employing cysteine residue modifications in the presence of a denaturant, and at a partially folded state. The partially folded monomeric CK (PF-CK) was aggregated with kinetic order, which was mainly caused by the hydrophobic surface interactions between the CK subunits. The artificial chaperone, described as a SDS-cyclodextrin, was applied to prevent aggregation as well as to refold the PF-CK: SDS treatment onto the monomeric CK can significantly block aggregation and can be successfully refolded in the solutions containing cyclodextrins and DTT. Three types of cyclodextrins such as alpha-, beta-, and gamma-cyclodextrins were applied to strip SDS from the enzyme molecule, and each kinetic course was measured. The intrinsic fluorescence changes showed that reactivation occurred and this accompanied the conformational changes. The size exclusion chromatography detected the variously trapped monomeric CKs such as the thiol residue modified PF-CK, the SDS-binding PF-CK, the cyclodextrin treated PF-CK, and the DTT treated SDS-binding PF-CK. Our study demonstrated monomer CK aggregation for the first time; we also demonstrated the complex reassociation of CK during refolding with the aid of the SDS-cyclodextrin, and these pathways followed first-order kinetics.

Interplay between carrier and impurity concentrations in annealed Ga1-xMnxAs: intrinsic anomalous hall effect

Investigating the scaling behavior of annealed Ga1-xMnxAs anomalous Hall coefficients, we note a universal crossover regime where the scaling behavior changes from quadratic to linear. Furthermore, measured anomalous Hall conductivities in the quadratic regime when properly scaled by carrier concentration remain constant, spanning nearly a decade in conductivity as well as over 100 K in T_[C] and comparing favorably to theoretically predicated values for the intrinsic origins of the anomalous Hall effect. Both qualitative and quantitative agreements strongly point to the validity of new equations of motion including the Berry phase contributions as well as the tunability of the anomalous Hall effect.

Complex inhibition of tyrosinase by thiol-composed Cu2+ chelators: a clue for designing whitening agents

The inhibition of tyrosinase has attracted considerable attention for potential medicinal and cosmetic applications, as well as in agriculture. This study investigated the inhibition effects of thiol-associated Cu(2+) chelators and deduced a strategy for designing and/or selecting tyrosinase inhibitors. Among the several compounds tested, dithioglycerine (DTGC) was selected for further experiments on the inhibition kinetics on tyrosinase. Different types of tyrosinases derived from mushroom and from the transient overexpression in HEK293 cells were tested individually. The results showed that DTGC significantly inhibited human tyrosinase in a complex manner (slope-parabolic mixed-type inhibition), which was comparable to mushroom tyrosinase. The affinity of DTGC affinity to human tyrosinase was evaluated by setting up a K(i slope) equation. The results suggest that a Cu(2+) chelator modified with thiol groups has potential as a whitening agent. In addition, a strategy for designing and/or selecting tyrosinase inhibitors that target the active enzyme site was also suggested.

Photopolymerized check valve and its integration into a pneumatic pumping system for biocompatible sample delivery

In this paper, we present a simple check valve whose operation mimics that of venous valves. Our check valve has a mono-leaflet and is constructed via an in situ fabrication method inside the PDMS platform. For the smooth operation of the valve's leaflet, the elasticity and the shape of the leaflet and the lubrication between the leaflet and the channel surface are important. We used 4-hydroxybutyl acrylate (4-HBA) as an elastic and photopolymerizable leaflet material. We mixed the triton X-100 with the 4-HBA pre-polymer solution for the adequate lubrication of the leaflet. We constructed the micro-pumping system by combining two venous-like check valves with an oscillating polymeric diaphragm driven by pneumatic force, and measured the flow rate according to the change of pumping frequency. We also investigated the pump's feasibility as a delivery system of biocompatible materials by using mouse embryo fibroblast cells.

Capture of monomeric refolding intermediate of human muscle creatine kinase

Human muscle creatine kinase (CK) is an enzyme that plays an important physiological role in the energy metabolism of humans. It also serves as a typical model for studying refolding of proteins. A study of the refolding and reactivation process of guanidine chloride-denatured human muscle CK is described in the present article. The results show that the refolding process can be divided into fast and slow folding phases and that an aggregation process competes with the proper refolding process at high enzyme concentration and high temperature. An intermediate in the early stage of refolding was captured by specific protein molecules: the molecular chaperonin GroEL and alpha(s)-casein. This intermediate was found to be a monomer, which resembles the "molten globule" state in the CK folding pathway. To our knowledge, this is the first monomeric intermediate captured during refolding of CK. We propose that aggregation is caused by interaction between such monomeric intermediates. Binding of GroEL with this intermediate prevents formation of aggregates by decreasing the concentration of free monomeric intermediates, whereas binding of alpha(s)-casein with this intermediate induces more aggregation.