A chemoenzymatic strategy for site-selective functionalization of native peptides and proteins.

The emergence of new therapeutic modalities requires complementary tools for their efficient syntheses. Availability of methodologies for site-selective modification of biomolecules remains a long-standing challenge, given the inherent complexity and the presence of repeating residues that bear functional groups with similar reactivity profiles. We describe a bioconjugation strategy for modification of native peptides relying on high site selectivity conveyed by enzymes. We engineered penicillin G acylases to distinguish among free amino moieties of insulin (two at amino termini and an internal lysine) and manipulate cleavable phenylacetamide groups in a programmable manner to form protected insulin derivatives. This enables selective and specific chemical ligation to synthesize homogeneous bioconjugates, improving yield and purity compared to the existing methods, and generally opens avenues in the functionalization of native proteins to access biological probes or drugs.

Colloidal aggregation and the in vitro activity of traditional Chinese medicines.

Traditional Chinese Medicines (TCMs) have been the sole source of therapeutics in China for two millennia. In recent drug discovery efforts, purified components of TCM formulations have shown activity in many in vitro assays, raising concerns of promiscuity. Here, we investigated 14 bioactive small molecules isolated from TCMs for colloidal aggregation. At concentrations commonly used in cell-based or biochemical assay conditions, eight of these compounds formed particles detectable by dynamic light scattering and showed detergent-reversible inhibition against ß-lactamase and malate dehydrogenase, two counter-screening enzymes. When three of these compounds were tested against their literature-reported molecular targets, they showed similar reversal of their inhibitory activity in the presence of detergent. For three of the most potent aggregators, contributions to promiscuity via oxidative cycling were investigated; addition of 1 mM DTT had no effect on their activity, which is inconsistent with an oxidative mechanism. TCMs are often active at micromolar concentrations; this study suggests that care must be taken to control for artifactual activity when seeking their primary targets. Implications for the formulation of these molecules are considered.

Hyperthermia-conditioned OECs serum-free-conditioned medium induce NSC differentiation into neuron more efficiently by the upregulation of HIF-1 alpha and binding activity.

BACKGROUND: Recent studies provide solid evidence for the importance to delineate the combined transplantation of neural stem cells (NSCs) and olfactory ensheathing cells (OECs) for the repair of central nervous system injury. One of the limitations of this approach is that the proportion of neurons differentiated from NSCs still remains at low level. Thus, how to induce NSCs to differentiate into neurons more efficiently by OECs is an attractive problem, which needs attention to be resolved. In the present study, we investigated the effects of hyperthermia-conditioned OEC-conditioned medium (OCM) on induction of NSCs into nerve cells. METHODS: The conditioned medium, named 37OCM, 40OCM, and 40OCM+R (treated with HIF-1a inhibitor), were collected after OECs had been incubated at 37°C or 40°C for 6 hr, followed by incubation at 37°C for 42 hr; then, these conditioned medium were collected and used for NSC induction. RESULTS: Results of the present study demonstrated for the first time that 6 hr of hyperthermia (40°C) could induce OECs upregulation and the expression of hypoxia-inducible factor-1 alpha (HIF-1α). Moreover, compared with 37OCM and 40OCM+R, 40OCM could induce NSCs differentiation into neurons more efficiently, and this phenomenon is associated with the upregulation of HIF-1α after hyperthermia conditioning. CONCLUSION: The data implied that the secretory protein in OECs-cultured medium and upregulation of HIF-1α expression and binding activity induced by hyperthermia-conditioned OECs have synergistic effect to induce NSCs differentiation into a neural lineage.