Urea

About: Urea is a research topic. Over the lifetime, 21394 publications have been published within this topic receiving 382444 citations. The topic is also known as: carbamide & carbonic acid diamide.

Characterization of gelatin-immobilized pigeonpea urease and preparation of a new urea biosensor.

Abstract: Urease purified from pigeonpea seeds was immobilized on gelatin beads via cross-linking with glutaraldehyde The maximum immobilization (75%) was observed at 30 mg/ml gelatin, 0414 mg of enzyme/bead, 1% (v/v) glutaraldehyde and 4 degrees C Beads stored in 50 mM Tris/acetate buffer (pH 73) at 4 degrees C showed a half-life of 240 days and there was practically no leaching of enzyme (less than 2%) over a period of 30 days These beads can be reused more than 30 times (with 24 h intervals) without much loss of enzyme activity (ie less than 11%) The immobilized urease showed a shift in its optimum pH from 73 to 65 in Tris/acetate buffer Optimum temperature also shifted from 47 to 65 degrees C compared with the soluble enzyme Gelatin-immobilized pigeonpea urease had a higher K(m) (83 mM) than that of the soluble enzyme (30 mM) The time-dependent temperature inactivation pattern was also found to change from biphasic to monophasic kinetics The immobilized beads were used for the preparation of a new urea biosensor with a response time of less than 2 min At least 14 samples of urea can be measured with this biosensor within an hour The beads, as well as the biosensor, were used to analyse the urea content in clinical samples from the local clinical pathology laboratories The results obtained with the biosensor were strikingly similar to those obtained with the various commonly employed biochemical/autoanalyzer(R) methods used These immobilization studies also have a potential role in haemodialysis machines that maintain the urea level in kidney patients and in the construction of a portable/wearable kidney The easy availability of the pigeonpea urease, the ease of its immobilization on gelatin and a significantly lower cost of the urease described in the present study makes it a suitable product for future applications in therapeutics and diagnostics

A review of Ni based powder catalyst for urea oxidation in assisting water splitting reaction

Abstract: Water splitting has been regarded as a sustainable and environmentally-friendly technique to realize green hydrogen generation, while more energy is consumed due to the high overpotentials required for the anode oxygen evolution reaction. Urea electrooxidation, an ideal substitute, is thus received increasing attention in assisting water-splitting reactions. Note that highly efficient catalysts are still required to drive urea oxidation, and the facile generation of high valence state species is significant in the reaction based on the electrochemical-chemical mechanisms. The high cost and rareness make the noble metal catalysts impossible for further consideration in large-scale application. Ni-based catalysts are very promising due to their cheap price, facile structure tuning, good compatibility, and easy active phase formation. In the light of the significant advances made recently, herein, we reviewed the recent advances of Ni-based powder catalysts for urea oxidation in assisting water-splitting reaction. The fundamental of urea oxidation is firstly presented to clarify the mechanism of urea-assisted water splitting, and then the prevailing evaluation indicators are briefly expressed based on the electrochemical measurements. The catalyst design principle including synergistic effect, electronic effect, defect construction and surface reconstruction as well as the main fabrication approaches are presented and the advances of various Ni-based powder catalysts for urea assisted water splitting are summarized and discussed. The problems and challenges are also concluded for the Ni-based powder catalysts fabrication, the performance evaluation, and their application. Considering the key influencing factors for catalytic process and their application, attention should be given to structure−property relationship deciphering, novel Ni-based powder catalysts development and their construction in the real device; specifically, the effort should be directed to the Ni-based powder catalyst with multi-functions to simultaneously promote the fundamental steps and high anti-corrosion ability by revealing the local structure reconstruction as well as the integration in the practical application. We believe the current summarization will be instructive and helpful for the Ni-based powder catalysts development and understanding their catalytic action for urea-assisted hydrogen generation via water splitting technique. Advances and challenges of Ni based powder catalyst were reviewed for urea oxidation in assisting water-splitting reaction.

The electrophoresis of transferrins in urea/polyacrylamide gels.

Abstract: The denaturation of transferrin by urea has been studied by (a) electrophoresis in polyacrylamide gels incorporating a urea gradient, (b) measurements of the loss of iron-binding capacity and (c) u.v. difference spectrometry. In human serum transferrin and hen ovotransferrin the N-terminal and C-terminal domains of the iron-free protein were found to denature at different urea concentrations.