Selective Cu2+ binding, redox silencing, and cytoprotective effects of the small heat shock proteins alphaA- and alphaB-crystallin

Oxidative stress and Cu²⁺ have been implicated in several neurodegenerative diseases and in cataract. Oxidative stress, as well as Cu²⁺, is also known to induce the expression of the small heat shock proteins α-crystallins. However, the role of α-crystallins in oxidative stress and in Cu²⁺-mediated processes is not clearly understood. We demonstrate using fluorescence and isothermal titration calorimetry that α-crystallins (αA- and αB-crystallin and its phosphorylation mimic, 3DαB-crystallin) bind Cu²⁺ with close to picomolar range affinity. The presence of other tested divalent cations such as Zn²⁺, Mg²⁺, and Ca²⁺ does not affect Cu²⁺ binding, indicating selectivity of the Cu²⁺-binding site(s) in α-crystallins. Cu²⁺ binding induces structural changes and increase in the hydrodynamic radii of α-crystallins. Cu²⁺ binding increases the stability of α-crystallins towards guanidinium chloride-induced unfolding. Chaperone activity of αA-crystallin increases significantly upon Cu²⁺ binding. α-Crystallins rescue amyloid beta peptide, Aβ_1-40, from Cu²⁺-induced aggregation in vitro. α-Crystallins inhibit Cu²⁺-induced oxidation of ascorbate and, hence, prevent the generation of reactive oxygen species. Interestingly, α-synuclein, a Cu²⁺-binding protein, does not inhibit this oxidation process significantly. We find that the Cu²⁺-sequestering (or redox-silencing) property of α-crystallins confers cytoprotection. To the best of our knowledge, this is the first study to reveal high affinity (close to picomolar) for Cu²⁺ binding and redox silencing of Cu²⁺ by any heat shock protein. Thus, our study ascribes a novel functional role to α-crystallins in Cu²⁺ homeostasis and helps in understanding their protective role in neurodegenerative diseases and cataract.     

Differential regulation of cholera toxin-inhibited Na-H exchange isoforms by butyrate in rat ileum

Electroneutral Na absorption occurs in the intestine via sodium-hydrogen exchanger (NHE) isoforms NHE2 and NHE3. Bicarbonate and butyrate both stimulate electroneutral Na absorption through NHE. Bicarbonate- but not butyrate-dependent Na absorption is inhibited by cholera toxin (CT). Long-term exposure to butyrate also influences expression of apical membrane proteins in epithelial cells. These studies investigated the effects of short- and long-term in vivo exposure to butyrate on apical membrane NHE and mRNA, protein expression, and activity in rat ileal epithelium that had been exposed to CT. Ileal loops were exposed to CT in vivo for 5 h and apical membrane vesicles were isolated. 22Na uptake was measured by using the inhibitor HOE694 to identify NHE2 and NHE3 activity, and Western blot analyses were performed. CT reduced total NHE activity by 70% in apical membrane vesicles with inhibition of both NHE2 and NHE3. Reduced NHE3 activity and protein expression remained low following removal of CT but increased to control values following incubation of the ileal loop with butyrate for 2 h. In parallel there was a 40% decrease in CT-induced increase in cAMP content. In contrast, NHE2 activity partially increased following removal of CT and was further increased to control levels by butyrate. NHE2 protein expression did not parallel its activity. Neither NHE2 nor NHE3 mRNA content were affected by CT or butyrate. These results indicate that CT has varying effects on the two apical NHE isoforms, inhibiting NHE2 activity without altering its protein expression and reducing both NHE3 activity and protein expression. Butyrate restores both CT-inhibited NHE2 and NHE3 activities to normal levels but via different mechanisms.     

Effect of sesame oil on diuretics or Beta-blockers in the modulation of blood pressure, anthropometry, lipid profile, and redox status

The study was undertaken to investigate the effect of sesame oil in hypertensive patients who were on antihypertensive therapy either with diuretics (hydrochlorothiazide) or ß-blockers (atenolol). Thirty-two male and 18 female patients aged 35 to 60 years old were supplied sesame oil (Idhayam gingelly oil) and instructed to use it as the only edible oil for 45 days. Blood pressure, anthropometry, lipid profile, lipid peroxidation, and enzymic and non-enzymic antioxidants were measured at baseline and after 45 days of sesame oil substitution. Substitution of sesame oil brought down systolic and diastolic blood pressure to normal. The same patients were asked to withdraw sesame oil consumption for another 45 days, and the measurements were repeated at the end of withdrawal period. Withdrawal of sesame oil substitution brought back the initial blood pressure values. A significant reduction was noted in body weight and body mass index (BMI) upon sesame oil substitution. No significant alterations were observed in lipid profile except triglycerides. Plasma levels of sodium reduced while potassium elevated upon the substitution of sesame oil. Lipid peroxidation (thiobarbituric acid reactive substances [TBARS]) decreased while the activities of superoxide dismutase (SOD), catalase (CAT), and the levels of vitamin C, vitamin E, ß-carotene, and reduced glutathione (GSH) were increased. The results suggested that sesame oil as edible oil lowered blood pressure, decreased lipid peroxidation, and increased antioxidant status in hypertensive patients.     

Self-assembly of a peptide sequence,EKKE, composed of exclusively charged amino acids: Role of charge in morphology and lead binding

The self-assembly of peptides is influenced by their amino acid sequence and other factors including pH, charge, temperature, and solvent. Herein, we explore whether a four-residue sequence, EKKE, consisting of exclusively charged amino acids shows the propensity to form self-assembled ordered nanostructures and whether the overall charge plays any role in morphological and functional properties. From a combination of experimental data provided by Thioflavin T fluorescence, Congo red absorbance, circular dichroism spectroscopy, dynamic light scattering, field emission-scanning electron microscopy, atomic force microscopy, and confocal microscopy, it is clear that the all-polar peptide and charged EKKE sequence shows a pH-dependent tendency to form amyloid-like structures, and the self-assembled entities under acidic, basic and neutral conditions exhibit morphological variation. Additionally, the ability of the self-assembled amyloid nanostructures to bind to the toxic metal, lead (Pb²⁺), was demonstrated from the analysis of the ultraviolet absorbance and X-ray photoelectron spectroscopy data. The modulation at the sequence level for the amyloid-forming EKKE scaffold can further extend its potential role not only in the remediation of other toxic metals but also towards biomedical applications.     

A large proportion of North American net ecosystem production is offset by emissions from harvested products,river/stream evasion,and biomass burning

Diagnostic carbon cycle models produce estimates of net ecosystem production (NEP, the balance of net primary production and heterotrophic respiration) by integrating information from (i) satellite‐based observations of land surface vegetation characteristics; (ii) distributed meteorological data; and (iii) eddy covariance flux tower observations of net ecosystem exchange (NEE) (used in model parameterization). However, a full bottom‐up accounting of NEE (the vertical carbon flux) that is suitable for integration with atmosphere‐based inversion modeling also includes emissions from decomposition/respiration of harvested forest and agricultural products, CO₂ evasion from streams and rivers, and biomass burning. Here, we produce a daily time step NEE for North America for the year 2004 that includes NEP as well as the additional emissions. This NEE product was run in the forward mode through the CarbonTracker inversion setup to evaluate its consistency with CO₂ concentration observations. The year 2004 was climatologically favorable for NEP over North America and the continental total was estimated at 1730 ± 370 TgC yr^?1 (a carbon sink). Harvested product emissions (316 ± 80 TgC yr^?1), river/stream evasion (158 ± 50 TgC yr^?1), and fire emissions (142 ± 45 TgC yr^?1) counteracted a large proportion (35%) of the NEP sink. Geographic areas with strong carbon sinks included Midwest US croplands, and forested regions of the Northeast, Southeast, and Pacific Northwest. The forward mode run with CarbonTracker produced good agreement between observed and simulated wintertime CO₂ concentrations aggregated over eight measurement sites around North America, but overestimates of summertime concentrations that suggested an underestimation of summertime carbon uptake. As terrestrial NEP is the dominant offset to fossil fuel emission over North America, a good understanding of its spatial and temporal variation – as well as the fate of the carbon it sequesters ─ is needed for a comprehensive view of the carbon cycle.     

Potent biphenyl- and 3-phenyl pyridine-based inhibitors of acetyl-CoA carboxylase

We report the synthesis and enzymatic evaluation of potent inhibitors of acetyl-CoA carboxylases (ACCs) containing biphenyl or 3-phenyl pyridine cores. These compounds inhibit both ACC1 and ACC2, or are moderately selective for either enzyme, depending on side chain substitution. Typical activities of the most potent compounds in this class are in the low double-digit to single-digit nanomolar range in in vitro assays using human ACC1 and ACC2 enzymes.     

Synthesis and screening of (E)-1-(β-D-galactopyranosyl)-4-(aryl)but-3-ene-2-one against Mycobacterium tuberculosis

A series of galactose-derived aryl enones were synthesised and screened against Mycobacterium tuberculosis H₃₇Rv. Preliminary results were promising with MIC values in the range 1.56-12.5 μg/mL.     

Electronic and Defective Engineering of Electrospun CaMnO3 Nanotubes for Enhanced Oxygen Electrocatalysis in Rechargeable Zinc–Air Batteries

Rational design and massive production of bifunctional catalysts with superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are essential for developing metal–air batteries and fuel cells. Herein, controllable large‐scale synthesis of sulfur‐doped CaMnO₃ nanotubes is demonstrated via an electrospinning technique followed by calcination and sulfurization treatment. The sulfur doping can not only replace oxygen atoms to increase intrinsic electrical conductivity but also introduce abundant oxygen vacancies to provide enough catalytically active sites, which is further demonstrated by density functional theory calculation. The resulting sulfur‐modified CaMnO₃ (CMO/S) exhibits better electrocatalytic activity for ORR and OER in alkaline solution with higher stability performance than the pristine CMO. These results highlight the importance of sulfur treatment as a facile yet effective strategy to improve the ORR and OER catalytic activity of the pristine CaMnO₃. As a proof‐of‐concept, a rechargeable Zn–air battery using the bifunctional catalyst exhibits a small charge–discharge voltage polarization, and long cycling life. Furthermore, a solid‐state flexible and rechargeable Zn–air battery gives superior discharge–charge performance and remarkable stability. Therefore, the CMO/S nanotubes might be a promising replacement to the Pt‐based electrocatalysts for metal–air batteries and fuel cells.