https://commons.ufh.ac.za/vital/access/manager/Index en-us 5 https://commons.ufh.ac.za/vital/access/manager/Repository/vital:45268 Wed 16 Mar 2022 10:18:30 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:30590 Wed 12 May 2021 23:10:41 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:29926 Wed 12 May 2021 19:50:04 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:29928 Wed 12 May 2021 19:14:28 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:29116 Wed 12 May 2021 19:14:06 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:29118 Wed 12 May 2021 18:23:20 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41337 Wed 12 May 2021 15:02:23 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:42174 Wed 12 May 2021 15:00:21 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41377 Wed 12 May 2021 14:34:09 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41484 Wed 12 May 2021 14:28:57 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:41163 Wed 12 May 2021 13:49:36 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:62598 Thu 16 Mar 2023 11:26:36 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:29119 Thu 13 May 2021 16:04:33 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:30589 50Îll viability at concentrations≤ 160μg/mL, however the conjugates showed<50% cell viabilityatconcentrations≤ 160μg/mLprobably due to the enhanced singlet oxygen quantum yield. The findings from this work show the importance of linking photosensitises such as phthalocyanines to metal nanoparticles for the enhancement ofsinglet oxygen quantum yield and ultimately the photodynamic effect.]]> Thu 13 May 2021 08:10:17 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:35406 Thu 13 May 2021 06:50:34 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:34528 Thu 13 May 2021 00:32:13 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:46417 Thu 10 Feb 2022 10:51:19 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:28063 90%) sequence similarity between BSCOMT and human soluble COMT (HSCOMT). BSCOMT was partially purified to 7.78 fold, 1.65% yield and had a specific activity of 0.052 U/mg. It had pH and temperature optima of 8.5 and 40oC, respectively. The Km, Vmax, Kcat and Kcat/Km towards esculetin methylation were respectively 1.475±0.130 pM, 0.0353±0.001 pmol/ml/min, 1.748 x 10-2±5.0x10-4 min-1 and 1.18x10-2 M-1. min-1. HSCOMT was expressed in Escherichia coli BL21(DE3) which showed optimal activity for esculetin methylation at pH and temperature of 7.0 and 30°C, respectively. It was purified to 5.62 fold, 22.6% yield with a specific activity of 3.85 U/mg. HSCOMT kinetic plots, upon incubation of the reaction mixture at 30°C for 5 min before addition of SAM was hyperbolic with Km, Vmax, Kcat and Kcat/Km values of 1.79 pM, 0.412 pmol/ml/min, 2.08 min-1 and 1.165 M-1. min-1, respectively. AuNPs and AgNPs showed a concentration dependent inhibition of HSCOMT activity upon increasing the 5 min incubation time to 1 h. Interestingly, HSCOMT kinetics, with 1 h incubation at 30°C, showed a sigmoidal curve, as well as increased activity. Incubation of the reaction mixture in the presence of 60 pM AuNPs and/or AgNPs for 1 hreversed the observed sigmoidal to a hyperbolic curve, with kinetic parameters comparable to those of 5 min incubation. SDS-PAGE analyses of HSCOMT after the kinetic experiments showed the enzyme incubated for 5 min as a monomer, while that which was incubated for 1 h migrated substantially as dimer. However, the HSCOMT incubated for 1 h in the presence of 60 pM AuNPs and/or AgNPs migrated as a monomer. This indicated that the extension of the incubation period allowed the dimerization of HSCOMT, which exhibited sigmoidal kinetics and higher activity. The presence of NPs impeded the HSCOMT dimerization which decreased the activity. Varying the concentration of SAM suggested that SAM had an allosteric modulatory effect on HSCOMT. Absorption spectroscopy indicated adsorption of HSCOMT on the gold and silver NP surfaces and the formation of NPs-HSCOMT corona. Fluorescence spectroscopy showed that the interaction of HSCOMT with both gold and silver NPs was governed by a static quenching mechanism, implying the formation of a non-fluorescent fluorophore-NP complex at the ground state. Further fluorometric analyses indicated that both gold and silver NPs had contact with Trp143; that the interactions were spontaneous and were driven by electrostatic interactions. Fourier transform infrared spectroscopic studies showed the adsorption of HSCOMT of the NPs surfaces to cause relaxation of the enzyme’s B-sheet structures. Molecular docking studies indicated involvement of largely hydrophilic amino acids, with the interacting distances of less than 3.5A. These findings signify the potential of nanotechnology in the control of COMT catalytic activity for the management of the COMT-related disorders.]]> Mon 13 Mar 2023 14:31:23 SAST ]]> https://commons.ufh.ac.za/vital/access/manager/Repository/vital:72824 Fri 31 May 2024 10:41:16 SAST ]]>