Tulane University

About: Tulane University is a education organization based out in New Orleans, Louisiana, United States. It is known for research contribution in the topics: Population & Blood pressure. The organization has 24478 authors who have published 47205 publications receiving 1944993 citations. The organization is also known as: University of Louisiana.

Enantioselective Direct-Addition of Terminal Alkynes to Imines Catalyzed by Copper(I)pybox Complex in Water and in Toluene

Abstract: Highly enantioselective direct alkyne-imine additions catalyzed by Cu(I)OTf and Evan's pybox ligands were developed in water and in toluene. The process is simple and provides a diverse range of propargylic amine in high ee and good yield.

Antimicrobial Peptides: Successes, Challenges and Unanswered Questions

Abstract: Multidrug antibiotic resistance is an increasingly serious public health problem worldwide. Thus, there is a significant and urgent need for the development of new classes of antibiotics that do not induce resistance. To develop such antimicrobial compounds, we must look toward agents with novel mechanisms of action. Membrane-permeabilizing antimicrobial peptides (AMPs) are good candidates because they act without high specificity toward a protein target, which reduces the likelihood of induced resistance. Understanding the mechanism of membrane permeabilization is crucial for the development of AMPs into useful antimicrobial agents. Various models, some phenomenological and others more quantitative or semimolecular, have been proposed to explain the action of AMPs. While these models explain many aspects of AMP action, none of the models captures all of the experimental observations, and significant questions remain unanswered. Here, we discuss the state of the field and pose some questions that, if answered, could speed the discovery of clinically useful peptide antibiotics.

The crystal structure of the GroES co-chaperonin at 2.8 Å resolution

Abstract: The GroES heptamer forms a dome, approximately 75 A in diameter and 30 A high, with an 8 A orifice in the centre of its roof. The 'mobile loop' segment, previously identified as a GroEL binding determinant, is disordered in the crystal structure in six subunits; the single well-ordered copy extends from the bottom outer rim of the GroES dome, suggesting that the cavity within the dome is continuous with the polypeptide binding chamber of GroEL in the chaperonin complex.

Angiogenic effects of human multipotent stromal cell conditioned medium activate the PI3K-Akt pathway in hypoxic endothelial cells to inhibit apoptosis, increase survival, and stimulate angiogenesis.

Abstract: Recent reports indicated that vascular remodeling and angiogenesis are promoted by conditioned medium from the cells referred to as multipotent stromal cells (MSCs). However, the molecular events triggered by MSC-conditioned medium (CdM) were not defined. We examined the effects of CdM from human MSCs on cultures of primary human aortic endothelial cells (HAECs). The CdM inhibited hypoxia-induced apoptosis and cell death of HAECs. It also promoted tube formation by HAECs in an assay in vitro. Conditioned medium from multipotent stromal cells incubated under hypoxic conditions in serum-free endothelial basal medium for 2 days (CdM(Hyp)) from hypoxic culture of MSCs was more effective than conditioned medium from MSCs incubated under normoxic conditions in serum-free endothelial basal medium for 2 days from normoxic cultures of MSCs, an observation in part explained by its higher content of antiapoptotic and angiogenic factors, such as interleukin (IL)-6, vascular endothelial growth factor (VEGF), and monocyte chemoattractant protein (MCP)-1. The effects of CdM(Hyp) on hypoxic HAECs were partially duplicated by the addition of IL-6 in a dose-dependent manner; however, anti-IL-6, anti-MCP-1, and anti-VEGF blocking antibodies added independently did not attenuate the effects. Also, addition of CdM(Hyp) activated the PI3K-Akt pathway; the levels of p-Akt and several of its downstream targets were increased by CdM(Hyp), and both the increase in p-Akt and the increase in angiogenesis were blocked by an inhibitor of PI3K-Akt or by expression of a dominant negative gene for PI3K. CdM(Hyp) also increased the levels of p-extracellular signal-regulated kinase (ERK), but there was a minimal effect on p-signal transducer and activator of transcription-3, and an inhibitor of the ERK1/2 pathway had no effect on hypoxia-induced apoptosis of the HAECs. The results are consistent with suggestions that administration of MSCs or factors secreted by MSCs may provide a therapeutic method of decreasing apoptosis and enhancing angiogenesis.

Accurate density functional for the energy: Real-space cutoff of the gradient expansion for the exchange hole.

Abstract: The density-gradient expansion of the fermion exchange hole is analyzed in real space. Unlike the local-density approximation, the second-order gradient-expansion approximation is found to violate two important properties of the exact hole: The exact hole is negative everywhere, and represents a deficit of one electron. Imposition of these exact constraints leads to an accurate new density functional for the exchange energy. Residual errors in the exchange energy for atoms are about 1% of this quantity. The new functional approximation may be generalized to include correlation.