Neuroprotective Potential of Biphalin, Multireceptor Opioid Peptide, Against Excitotoxic Injury in Hippocampal Organotypic Culture

Biphalin is a dimeric opioid peptide that exhibits affinity for three types of opioid receptors (MOP, DOP and KOP). Biphalin is undergoing intensive preclinical study. It was recognized that activation of δ-opioid receptor elicits neuroprotection against brain hypoxia and ischemia. We compare the effect of biphalin and morphine and the inhibition of opioid receptors by naltrexone on survival of neurons in rat organotypic hippocampal cultures challenged with NMDA. Findings: (1) 0.025–0.1 μM biphalin reduces NMDA-induced neuronal damage; (2) biphalin neuroprotection is abolished by naltrexone; (3) reduced number of dead cells is shown even if biphalin is applied with delay after NMDA challenge

Interference of H-bonding and substituent effects in nitro- and hydroxy-substituted salicylaldehydes

Two intramolecular interactions, i.e., (1) hydrogen bond and (2) substituent effect, were analyzed and compared. For this purpose, the geometry of 4- and 5-X-substituted salicylaldehyde derivatives (X = NO2, H or OH) was optimized by means of B3LYP/6-311 + G(d,p) and MP2/aug-cc-pVDZ methods. The results obtained allowed us to show that substituents (NO2 or OH) in the para or meta position with respect to either OH or CHO in H-bonded systems interact more strongly than in the case of di-substituted species: 4- and 3-nitrophenol or 4- and 3-hydroxybenzaldehyde by ∼31%. The substituent effect due to the intramolecular charge transfer from the para-counter substituent (NO2) to the proton-donating group (OH) is ∼35% greater than for the interaction of para-OH with the proton-accepting group (CHO). The total energy of H-bonding for salicylaldehyde, and its derivatives, is composed of two contributions: ∼80% from the energy of H-bond formation and ∼20% from the energy associated with reorganization of the electron structure of the systems in question

A SNIFTIRS study of the adsorption of pyridine at the Au(111) electrode–solution interface

Subtractively normalized interfacial Fourier transform infrared spectroscopy (SNIFTIRS) has been applied to study coordination of the pyridine molecules to the Au(111) electrode surface. The IR spectra have been recorded using both p- and s-polarized radiation. The ratio of the integrated band intensities for the spectra recorded with p- and s-polarized light was then used to study changes in the surface coordination of pyridine molecules. We have derived an expression describing the dependence of this ratio on the tilt angle. We have described the orientation of the adsorbed molecule in terms of angles formed between the surface, and: (i) C2v axis of the pyridine molecule, (ii) the direction in plane of the molecule and normal to the C2v axis. We were able to demonstrate that both angles increase by moving from negative to positive potentials. This result indicates that the pyridine molecule not only stands up at positive potentials but also its plane rotates somewhat with respect to the electrode surface