Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

ESI‐MS/MS of expanded porphyrins: a look into their structure and aromaticity

Electrospray mass spectrometry/mass spectrometry was used to investigate the gas‐phase properties of protonated expanded porphyrins, in order to correlate those with their structure and conformation. We have selected five expanded meso‐pentafluorophenyl porphyrins, respectively, a pair of oxidized/reduced fused pentaphyrins (22 and 24 π electrons), a pair of oxidized/reduced regular hexaphyrins (26 and 28 π electrons) and a regular doubly N‐fused hexaphyrin (28 π electrons). The gas‐phase behavior of the protonated species of oxidized and reduced expanded porphyrins is different. The oxidized species (aromatic Hückel systems) fragment more extensively, mainly by the loss of two HF molecules. The reduced species (Möbius aromatic or Möbius‐like aromatic systems) fragment less than their oxidized counterparts because of their increased flexibility. The protonated regular doubly fused hexaphyrin (non‐aromatic Hückel system) shows the least fragmentation even at higher collision energies. In general, cyclization through losses of HF molecules decreases from the aromatic Hückel systems to Möbius aromatic or Möbius‐like aromatic systems to non‐aromatic Hückel systems and is related to an increase in conformational distortion. Copyright © 2016 John Wiley & Sons, Ltd.     

Imaging the binding ability of proteins immobilized on surfaces with different orientations by using liquid crystals

We report an investigation of the binding ability of a protein immobilized on surfaces with different orientations but in identical interfacial microenvironments. The surfaces present mixed self-assembled monolayers (SAMs) of 11-[19-carboxymethylhexa(ethylene glycol)]undecyl-1-thiol, 1, and 11-tetra(ethylene glycol) undecyl-1-thiol, 2. Whereas 2 is used to define an interfacial microenvironment that prevents nonspecific adsorption of proteins, 1 was activated by two different schemes to immobilize ribonuclease A (RNase A) in either a preferred orientation or random orientations. The binding of the ribonuclease inhibitor protein (RI) to RNase A on these surfaces was characterized by using ellipsometry and the orientational behavior of liquid crystals. Ellipsometric measurements indicate identical extents of immobilization of RNase A via the two schemes. Following incubation of both surfaces with RI, however, ellipsometric measurements indicate a 4-fold higher binding ability of the RNase A immobilized with a preferred orientation over RNase A immobilized with a random orientation. The higher binding ability of the oriented RNase A over the randomly oriented RNase A was also apparent in the orientational behavior of nematic liquid crystals of 4-cyano-4'-pentylcyanobiphenyl (5CB) overlayed on these surfaces. These results demonstrate that the orientations of proteins covalently immobilized in controlled interfacial microenvironments can influence the binding activities of the immobilized proteins. Results reported in this article also demonstrate that the orientational states of proteins immobilized at surfaces can be distinguished by examining the optical appearances of liquid crystals.     

Investigating the vortex melting phenomenon in BSCCO crystals using magneto-optical imaging technique

Using a novel differential magneto-optical imaging technique we investigate the phenomenon of vortex lattice melting in crystals of Bi₂Sr₂CaCu₂O₈ (BSCCO). The images of melting reveal complex patterns in the formation and evolution of the vortex solid-liquid interface with varying field (H)/temperature (T). We believe that the complex melting patterns are due to a random distribution of material disorder/inhomogeneities across the sample, which create fluctuations in the local melting temperature or field value. To study the fluctuations in the local melting temperature/field, we have constructed maps of the melting landscape T _m(H, r), viz., the melting temperature (T _m) at a given location (r) in the sample at a given field (H). A study of these melting landscapes reveals an unexpected feature: the melting landscape is not fixed, but changes rather dramatically with varying field and temperature along the melting line. It is concluded that the changes in both the scale and shape of the landscape result from the competing contributions of different types of quenched disorder which have opposite effects on the local melting transition.     

Energy dependence of multiplicity in proton-nucleus collisions and models of multiparticle production

This is a continuation of our earlier investigation (Gurtuet al 1974Phys. Lett. 50 B 391) on multiparticle production in proton-nucleus collisions based on an exposure of emulsion stack to 200 GeV/c beam at the NAL. It is found that the ratioR _em = 〈n _s〉/〈n _ch〉, where 〈n _ch〉 is the charged particle multiplicity in pp-collisions, increases slowly from about 1 at 10 GeV/c to 1·6 at 68 GeV/c and attains a constant value of 1·71 ± 0·04 in the region 200 to 8000 GeV/c. Furthermore,R _em = 1·71 implies an effectiveA-dependence ofR _A =A ^0.18,i.e., a very weak dependence. Predictions ofR _em on various models are discussed and compared with the emulsion data. Data seem to favour models of hadron-nucleon collisions in which production of particles takes place through adouble step mechanism,e.g., diffractive excitation, hydrodynamical and energy flux cascade as opposed to models which envisage instantaneous production.     

Tri-partite complex for axonal transport drug delivery achieves pharmacological effect

Background

Targeted delivery of pharmaceutical agents into selected populations of CNS (Central Nervous System) neurons is an extremely compelling goal. Currently, systemic methods are generally used for delivery of pain medications, anti-virals for treatment of dermatomal infections, anti-spasmodics, and neuroprotectants. Systemic side effects or undesirable effects on parts of the CNS that are not involved in the pathology limit efficacy and limit clinical utility for many classes of pharmaceuticals. Axonal transport from the periphery offers a possible selective route, but there has been little progress towards design of agents that can accomplish targeted delivery via this intraneural route. To achieve this goal, we developed a tripartite molecular construction concept involving an axonal transport facilitator molecule, a polymer linker, and a large number of drug molecules conjugated to the linker, then sought to evaluate its neurobiology and pharmacological behavior.

Results

We developed chemical synthesis methodologies for assembling these tripartite complexes using a variety of axonal transport facilitators including nerve growth factor, wheat germ agglutinin, and synthetic facilitators derived from phage display work. Loading of up to 100 drug molecules per complex was achieved. Conjugation methods were used that allowed the drugs to be released in active form inside the cell body after transport. Intramuscular and intradermal injection proved effective for introducing pharmacologically effective doses into selected populations of CNS neurons. Pharmacological efficacy with gabapentin in a paw withdrawal latency model revealed a ten fold increase in half life and a 300 fold decrease in necessary dose relative to systemic administration for gabapentin when the drug was delivered by axonal transport using the tripartite vehicle.

Conclusion

Specific targeting of selected subpopulations of CNS neurons for drug delivery by axonal transport holds great promise. The data shown here provide a basic framework for the intraneural pharmacology of this tripartite complex. The pharmacologically efficacious drug delivery demonstrated here verify the fundamental feasibility of using axonal transport for targeted drug delivery.     

Using liquid crystals to report membrane proteins captured by affinity microcontact printing from cell lysates and membrane extracts

The chemical heterogeneity of proteins makes development of general and facile surface-based methods for protein analysis a substantial challenge, particularly when analyzing transmembrane proteins. Here, we report a simple surface-based procedure that permits detection of transmembrane proteins from crude cell lysates and cell membrane extracts. The method relies on the use of thermotropic liquid crystals to amplify and report the presence of the transmembrane proteins captured by an affinity ligand on the surface of an elastomeric stamp. A merit of this approach is that the proteins can be imaged on surfaces without requiring the use of matched pairs of antibodies, labels, or complex instrumentation. Detection of epidermal growth factor receptor, a transmembrane glycoprotein, is demonstrated.     

Influence of 4-cyano-4'-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces

We report two methods that involve tailoring of the chemical composition of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl to achieve control over the orientational ordering of the liquid crystal on chemically functionalized surfaces. The first method involves the direct addition of 4-cyano-4'-biphenylcarboxylic acid to 4-cyano-4'-pentylbiphenyl. The second method involves exposure of 4-cyano-4'-pentylbiphenyl to ultraviolet light and photochemical generation of a range of products, including 4-cyano-4'-biphenylcarboxylic acid. The addition of the acid or exposure to ultraviolet light accelerated the rate at which the liquid crystal exhibited an orientational transition from planar to perpendicular (homeotropic) alignment on surfaces presenting ammonium groups. The appearance of the homeotropic orientation of the UV-treated 4-cyano-4'-pentylbiphenyl on ammonium-terminated surfaces was dependent on the thickness of the film of liquid crystal (13-50 mum), consistent with a dipolar coupling between the liquid crystal and the electric field associated with an electrical double layer generated at the ammonium surface. Although the addition of 4-cyano-4'-biphenylcarboxylic acid or UV treatment of the liquid crystal also promoted homeotropic orientations on surfaces presenting hydroxyl groups, the orientations of the UV-treated liquid crystal on the hydroxyl-terminated surface did not change with thickness of the film of liquid crystal in the manner observed on the ammonium-terminated surfaces. The latter result indicates that the mechanism leading to homeotropic anchoring on hydroxyl-terminated surfaces is distinct from that on ammonium-terminated surfaces. Measurements performed using polarization modulation infrared reflection-absorption spectroscopy suggest that hydrogen bonding between the 4-cyano-4'-biphenylcarboxylic acid and the hydroxyl-terminated surface is responsible for the homeotropic anchoring on the surface. Finally, the orientation of the liquid crystal on methyl-terminated surfaces was not influenced by the addition of 4-cyano-4'-biphenylcarboxylic acid nor UV treatment. These results illustrate how the chemical composition of liquid crystals can be manipulated to achieve control over their ordering on surfaces that possess chemical functionality relevant to the development of liquid crystal-based sensors and diagnostic tools. We illustrate the utility of this approach by using the tailored liquid crystal to amplify and optically transduce the presence of proteins arrayed on ammonium-terminated surfaces.