Evaluation of silver nanoparticles synthetic potential of Couroupita guianensis Aubl., flower buds extract and their synergistic antibacterial activity

The present investigation demonstrates Couroupita guianensis flower buds extract mediated synthesis of stable silver nanoparticles (AgNPs). Instant formation of AgNPs was primarily confirmed by the appearance of yellowish brown colour and characteristic silver SPR band in the UV–visible spectrum. Elemental and crystalline natures of the AgNPs were identified from EDX and XRD pattern, respectively. Spherical morphology and the mono-disparity were revealed from TEM and AFM images. The particle size ranged from 5 to 30 nm and average size of 17 nm was consistent in XRD, TEM and AFM measurements. Possible reduction and stabilizing agents, viz., phenolics, flavonoids and proteins were identified from the characteristic FTIR peaks representing their functional groups. The strong antibacterial activity of synthesized AgNPs against Gram-positive and Gram-negative bacteria exhibited the potential for the formulation of synergistic bactericides by combining antibacterial properties of Couroupita flower buds extract and silver salts for biomedical applications.

Allosteric nature of P2X receptor activation probed by photoaffinity labelling

BACKGROUND AND PURPOSE

In P2X receptors, agonist binding at the interface between neighbouring subunits is efficiently transduced to ion channel gating. However, the relationship between binding and gating is difficult to study because agonists continuously bind and unbind. Here, we covalently incorporated agonists in the binding pocket of P2X receptors and examined how binding site occupancy affects the ability of the channel to gate.

EXPERIMENTAL APPROACH

We used a strategy for tethering agonists to their ATP-binding pocket, while simultaneously probing ion channel gating using electrophysiology. The agonist 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP), a photoaffinity analogue of ATP, enabled us to trap rat homomeric P2X2 receptor and a P2X2/1 receptor chimera in different agonist-bound states. UV light was used to control the degree of covalent occupancy of the receptors.

KEY RESULTS

Irradiation of the P2X2/1 receptor chimera - BzATP complex resulted in a persistent current that lasted even after extensive washout, consistent with photochemical tethering of the agonist BzATP and trapping of the receptors in an open state. Partial labelling with BzATP primed subsequent agonist binding and modulated gating efficiency for both full and partial agonists.

CONCLUSIONS AND IMPLICATIONS

Our photolabelling strategy provides new molecular insights into the activation mechanism of the P2X receptor. We show here that priming with full agonist molecules leads to an increase in gating efficiency after subsequent agonist binding.

Chronic interstitial nephritis following parenteral copper sulfate poisoning

A 21-year-old male patient was admitted with acute renal failure and intravascular hemolysis following suicidal parenteral copper sulfate poisoning. He developed metabolic acidosis and septicemia; and was treated with intensive hemodialysis, blood transfusions and antibiotics. After remaining anuric for 4 weeks, his urine output gradually increased. However his renal functions improved only partially. Renal biopsy done 8 weeks after the episode showed chronic tubulo-interstitial nephritis (CIN). This is the first reported case showing CIN following acute copper sulfate intoxication.