Quantitative surface studies of protein adsorption by infrared spectroscopy. I. Correction for bulk concentrations

A method for correcting attenuated total reflectance (ATR) infrared spectra of surface-adsorbed proteins for the contribution of proteins in the bulk solution has been demonstrated. This procedure estimates the soluble protein contribution to the ir spectra from parameters determined from transmission experiments, and uses the absorbance of the water band in ATR as an internal reference. Based on this procedure, the soluble protein contribution to the total spectrum is estimated to range from approximately 3% for IgG or albumin in solution at 1 mg/ml, to approximately 35% when whole blood (from sheep) is adsorbed onto a 45 degrees germanium ATR crystal.     

CXCL14 is no direct modulator of CXCR4

C-X-C motif chemokine 12/C-X-C chemokine receptor type 4 (CXCL12/CXCR4) signaling is involved in ontogenesis, hematopoiesis, immune function and cancer. Recently, the orphan chemokine CXCL14 was reported to inhibit CXCL12-induced chemotaxis – probably by allosteric modulation of CXCR4. We thus examined the effects of CXCL14 on CXCR4 regulation and function using CXCR4-transfected human embryonic kidney (HEK293) cells and Jurkat T cells. CXCL14 did not affect dose–response profiles of CXCL12-induced CXCR4 phosphorylation, G protein-mediated calcium mobilization, dynamic mass redistribution, kinetics of extracellular signal-regulated kinase 1 (ERK1) and ERK2 phosphorylation or CXCR4 internalization. Hence, essential CXCL12-operated functions of CXCR4 are insensitive to CXCL14, suggesting that interactions of CXCL12 and CXCL14 pathways depend on a yet to be identified CXCL14 receptor.     

How Epigallocatechin Gallate Can Inhibit α-Synuclein Oligomer Toxicity in Vitro

Oligomeric species of various proteins are linked to the pathogenesis of different neurodegenerative disorders. Consequently, there is intense focus on the discovery of novel inhibitors, e.g. small molecules and antibodies, to inhibit the formation and block the toxicity of oligomers. In Parkinson disease, the protein α-synuclein (αSN) forms cytotoxic oligomers. The flavonoid epigallocatechin gallate (EGCG) has previously been shown to redirect the aggregation of αSN monomers and remodel αSN amyloid fibrils into disordered oligomers. Here, we dissect EGCG''s mechanism of action. EGCG inhibits the ability of preformed oligomers to permeabilize vesicles and induce cytotoxicity in a rat brain cell line. However, EGCG does not affect oligomer size distribution or secondary structure. Rather, EGCG immobilizes the C-terminal region and moderately reduces the degree of binding of oligomers to membranes. We interpret our data to mean that the oligomer acts by destabilizing the membrane rather than by direct pore formation. This suggests that reduction (but not complete abolition) of the membrane affinity of the oligomer is sufficient to prevent cytotoxicity.     

Nanoconfined gases,liquids and liquid crystals in porous materials

We propose here to give an overview of gases and liquids adsorption in the materials of Institute Lavoisier (MIL)-101(Cr), MIL-53(Cr) and silica materials. We present some recent results of systems of interests such as the H₂ adsorption in MIL-101(Cr) and CO₂ and H₂S adsorption in the MIL-53(Cr) material. In addition, we will examine the sensitivity in water force field for water adsorption in hydrophilic and hydrophobic silica nanopores and we evaluate the Gay–Berne liquid crystal adsorption in the smooth and rough pores.     

Biased and unbiased strategies to identify biologically active small molecules

Small molecules are central players in chemical biology studies. They promote the perturbation of cellular processes underlying diseases and enable the identification of biological targets that can be validated for therapeutic intervention. Small molecules have been shown to accurately tune a single function of pluripotent proteins in a reversible manner with exceptional temporal resolution. The identification of molecular probes and drugs remains a worthy challenge that can be addressed by the use of biased and unbiased strategies. Hypothesis-driven methodologies employs a known biological target to synthesize complementary hits while discovery-driven strategies offer the additional means of identifying previously unanticipated biological targets. This review article provides a general overview of recent synthetic frameworks that gave rise to an impressive arsenal of biologically active small molecules with unprecedented cellular mechanisms.     

Electromyographic responses of erector spinae and lower limb’s muscles to dynamic postural perturbations in patients with adolescent idiopathic scoliosis

The aim of this study was to evaluate electromyographic (EMG) responses of erector spinae (ES) and lower limbs’ muscles to dynamic forward postural perturbation (FPP) and backward postural perturbation (BPP) in patients with adolescent idiopathic scoliosis (AIS) and in a healthy control group. Ten right thoracic AIS patients (Cobb = 21.6 ± 4.4°) and 10 control adolescents were studied. Using bipolar surface electrodes, EMG activities of ES muscle at T10 (ES_T10) and L3 (ES_L3) levels, biceps femoris (BF), gastrocnemius lateralis (G) and rectus femoris (RF) muscles in the right and the left sides during FPP and BPP were evaluated. Muscle responses were measured over a 1s time window after the onset of perturbation. In FPP test, the EMG responses of right ES_T10, ES_L3 and BF muscles in the scoliosis group were respectively about 1.40 (p = 0.035), 1.43 (p = 0.07) and 1.45 (p = 0.01) times greater than those in control group. Also, in BPP test, at right ES_L3 muscle of the scoliosis group the EMG activity was 1.64 times higher than that in the control group (p = 0.01). The scoliosis group during FPP displayed asymmetrical muscle responses in ES_T10 and BF muscles. This asymmetrical muscle activity in response to FPP is hypothesized to be a possible compensatory strategy rather than an inherent characteristic of scoliosis.     

Surface behavior of apolipoprotein A-I and its deletion mutants at model lipoprotein interfaces

Apolipoprotein A-I (apoA-I) has a great conformational flexibility to exist in lipid-free, lipid-poor, and lipid-bound states during lipid metabolism. To address the lipid binding and the dynamic desorption behavior of apoA-I at lipoprotein surfaces, apoA-I, Δ(185-243)apoA-I, and Δ(1-59)(185-243)apoA-I were studied at triolein/water and phosphatidylcholine/triolein/water interfaces with special attention to surface pressure. All three proteins are surface active to both interfaces lowering the interfacial tension and thus increasing the surface pressure to modify the interfaces. Δ(185-243)apoA-I adsorbs much more slowly and lowers the interfacial tension less than full-length apoA-I, confirming that the C-terminal domain (residues 185-243) initiates the lipid binding. Δ(1-59)(185-243)apoA-I binds more rapidly and lowers the interfacial tension more than Δ(185-243)apoA-I, suggesting that destabilizing the N-terminal α-helical bundle (residues 1-185) restores lipid binding. The three proteins desorb from both interfaces at different surface pressures revealing that different domains of apoA-I possess different lipid affinity. Δ(1-59)(185-243)apoA-I desorbs at lower pressures compared with apoA-I and Δ(185-243)apoA-I indicating that it is missing a strong lipid association motif. We propose that during lipoprotein remodeling, surface pressure mediates the adsorption and partial or full desorption of apoA-I allowing it to exchange among different lipoproteins and adopt various conformations to facilitate its multiple functions.     

动态血糖监测在老年2型糖尿病患者降糖治疗中的应用价值

目的：通过对老年2型糖尿病患者进行动态血糖监测了解降糖治疗的疗效,评价动态血糖监测系统的应用价值,确定其在治疗老年2型糖尿病患者中的地位。方法：选取2008年8月至2013年8月住院的老年2型糖尿病患者95例,随机分为对照组48例和观察组47例,对照组行予常规的指尖血糖监测,观察组行动态血糖监测,比较两组患者血糖的控制情况。结果：观察组患者治疗后平均血糖、高血糖持续时间、低血糖持续时间、血糖最大波波动幅度、平均血糖波动幅度、血清糖化白蛋白及餐后2h血糖等与治疗前相比较比较,差异均有统计学意义,P〈0.05。对照组患者治疗后平均血糖、高血糖持续时间、低血糖持续时间、血糖最大波波动幅度、平均血糖波动幅度、血清糖化白蛋白及餐后2h血糖等与治疗前相比较比较,差异均无统计学意义,P〉0.05。两组患者空腹血糖治疗前、后差异均无统计学意义,P〉0.05。结论：动态血糖监测系统用于监测老年2型糖尿病患者的降糖治疗疗效优于常规血糖检测。     

Microbial production of enzymes: Nonlinear state and kinetic reaction rates estimation

The nonlinearity of the biotechnological processes and the absence of cheap and reliable instrumentation require an enhanced modelling effort and estimation strategies for the state and the kinetic parameters. This work approaches nonlinear estimation strategies for microbial production of enzymes, exemplified by using a process of lipase production from olive oil by Candida rugosa. First, by using a dynamical mathematical model of this process, an asymptotic observer which reconstructs the unavailable state variables is proposed. The design of this kind of observers is based on mass and energy balances without the knowledge of kinetics being necessary; only minimal information concerning the measured concentrations is used. Second, a nonlinear high-gain observer is designed for the estimation of imprecisely known kinetics of the bioprocess. An important advantage of this high-gain estimator is that the tuning is reduced to the calibration of a single parameter. Numerical simulations in various scenarios are provided in order to test the behaviour and performances of the proposed nonlinear estimation strategies.