Anti-Tyrosine polyclonal antibody

Tyrosinase is the key enzyme for the metabolism of tyrosine and inherently comprises both monophenolase activity and diphenolase activity. A real-time fluorometric assay method was established to exclusively monitor the monophenolase activity by eliminating interference from diphenolase reactions through a combination of borate and hydroxylamine. Synthetic matrices comprised of tyrosine and DOPA (L-3,4-dihydroxyphenylalanine) preincubated with tyrosinase with the consistent sum concentration of 70 mu M to mimic the monophenolase reaction mixture in borate buffer according to law of mass conservation. A matrix-matched calibration curve for determination of tyrosine was established using the synthetic matrices as standard sample to eliminate spectral interference from DOPA. The limit of detection (LOD) for tyrosine was 0.61 mu M. The time course for consumption of tyrosine was established to measure the initial velocity through real-time reading out the tyrosine fluorescence intensity of the reaction mixture in a cuvette in situ. The assay worked in the monophenolase activity range from 0.2839 to 1.7308 U mL(-1) with LOD of 0.0851 U mL(-1). The proposal sensing system successfully afforded a prospective potential for application in enzyme kinetics and screening of inhibitor.

Mesenchymal stem cell (MSC) transplantation has demonstrated its potential in repairing infarct heart tissue and recovering heart function after myocardial infarction (MI). However, its therapeutic effect is still limited due to poor MSC engraftment at the injury site whose tissue stiffness and local inflammation both dynamically and rapidly change after MI. Whether and how inflammatory cytokines could couple with stiffness change to affect MSC engraftment in the infarct zone still remain unclear. In this study, we characterized dynamic stiffness changes of and inflammatory cytokine expression in the infarct region of rat heart within a month after MI. We found that the tissue stiffness of the heart tissue gradually increased and peaked 21 days after MI along with the rapid upregulation of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and interleukin-1 beta (IL-1 beta) in the first 3 days, followed by a sharp decline. We further demonstrated in vitro that immobilized inflammatory cytokine IL-6 performed better than the soluble form in enhancing MSC adhesion to stiffened substrate through IL-6/src homology 2 (SH2) domain-containing tyrosine phosphatase-2 (SHP2)/integrin signaling axis. We also confirmed such mechano-immune coupling of tissue stiffness and inflammatory cytokines in modulating MSC engraftment in the rat heart after MI in vivo. Our study provides new mechanistic insights of mechanical-inflammation coupling to improve MSC mechanosensing and adhesion, potentially benefiting MSC engraftment and its clinical therapy for MI.