Purification and properties of cis-aconitic decarboxylase

Summary Lyophilized and stored in a deep-freeze, the mycelial material was found to retain cis-aconitic decarboxylase activity unimpaired at the end of 2 months. Mycelia could be stored also in the frozen condition but after squeezing hard to remove as much of adherent water as possible. Extracts with maximum cis-aconitic decarboxylase activity were obtained when the frozen or better the lyophilized mycelia of Aspergillus terreus were ground in a mortar with phosphate buffer using pyrex glass powder as abrasive. Cis-aconitic decarboxylase was purified 25-fold by fractionation with ammonium sulfate, starting from extracts of the mycelia in phosphate buffer. The purified enzyme was considerably more stable than the crude extracts to storage and dialysis. The optimum pH was 5.8 using 0.2 m phosphate buffer; Km value was 5×10^-3 m at pH 5.8 and 37°C. EDTA and 8-hydroxyquinoline activated the enzyme; all metals tested inhibited the enzyme, Zn⁺⁺ and Cu⁺⁺ leading to complete inactivation. Fluoride, arsenite and azide also inhibited the enzyme activity.     

Multi-layered Graphene Silica-Based Tunable Absorber for Infrared Wavelength Based on Circuit Theory Approach

Graphene can be utilized as a tunable material for a wide range of infrared wavelength regions due to its tunable conductivity property. In this paper, we use Y-shaped silver material resonator placed over the top of multiple graphene silica-layered structures to realize the perfect absorption over the infrared wavelength region. We propose four different designs by placing the graphene sheet over silica. The absorption and reflectance performance of the structures have been explored for 1500- to 1600-nm wavelength range. The proposed design also explores the absorption tunability of the structure for the different values of graphene chemical potential. We have reported the negative impedance for the perfect absorption for proposed metamaterial absorber structures. All the metamaterial absorbers have reported 99% of its absorption peaks in the infrared wavelength region. These designs can be used as a tunable absorber for narrowband and wideband applications. The proposed designs will become the basic building block of large photonics design which will be applicable for polariser, sensor, and solar applications.

     

Design of a New Peptide Substrate Probe of the Putative Biomarker Legumain with Potential Application in Prostate Cancer Diagnosis Ex Vivo

International Journal of Peptide Research and Therapeutics - The lysosomal endoprotease legumain (asparaginyl endoprotease) has been proposed as a putative biomarker in prostate tumours, in which...     

MsrA Efflux Pump Inhibitory Activity of Piper cubeba L.f. and its Phytoconstituents against Staphylococcus aureus RN4220

MsrA, an efflux pump belonging to ATP‐binding cassette (ABC) transporter family that conferred resistance to macrolides, was detected in Staphylococcus aureus strains. Herein, we report the isolation of phytoconstituents from Piper cubeba fruit methanol extract and investigated their efflux pump inhibitory potential against S. aureus MsrA pump. Four isolated compounds, viz. pellitorine, sesamin, piperic acid and tetrahydropiperine studied in combination with erythromycin in S. aureus RN4220, exhibited 2–8‐fold reduction in minimum inhibitory concentration (MIC) of erythromycin. Pellitorine and sesamin decreased MIC of erythromycin by 8‐fold. The real‐time fluorometry‐based efflux and accumulation studies of ethidium bromide (EtBr) on S. aureus RN4220 in the presence of these compounds showed reduced efflux and enhanced uptake, thus indicating inhibition of the efflux pump. Pellitorine showed significant post‐antibiotic effect of erythromycin. The results revealed that the primary mechanism of action of these compounds involves steady ATP production impairment.