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R Jelinek

Publications and source records attributed to R Jelinek.

At least 19 recordsLinked to original sources
PubMed2001

Rapid colorimetric detection of antibody-epitope recognition at a biomimetic membrane interface.

Biomolecular recognition of antigens and epitopes by antibodies is a fundamental event in the initiation of immune response and plays a central role in a variety of biochemical processes. Peptide binding requires, in many cases, presentation of the peptides at interfaces, such as protein surfaces, cellular membranes, and synthetic polymer surfaces. We describe a novel molecular system in which interactions between antibodies and peptide epitopes displayed at a biomimetic membrane interface can be detected through induction of visible, rapid color transitions. The colorimetric assembly consists of a phospholipid/polydiacetylene matrix anchoring a hydrophobic peptide displaying the epitope at its N-terminus. The colorimetric transitions observed in the assembly, corresponding to perturbation of the polydiacetylene framework, are induced only upon recognition of the displayed epitope by its specific antibody present in the aqueous solution. Significantly, the color changes occur after a single mixing step, without further chemical reactions or enzymatic processing. The new molecular system could be utilized for studying antigen-antibody interactions and peptide-protein recognition, epitope mapping, and rapid screening of biological and chemical libraries.

Antibodies, Monoclonal↗
PubMed2001

A new colorimetric assay for studying and rapid screening of membrane penetration enhancers.

PURPOSE: This work aims to demonstrate a novel chemical assay for rapid screening and analysis of the mode of action of membrane interaction by penetration enhancers. METHODS: The new bio-mimetic membrane assembly, consisting of supramolecular aggregates of lipids and conjugated polydiacetylene, undergoes visible and quantifiable blue-red color transitions upon interaction with penetration enhancers. RESULTS: The new colorimetric model has been employed to examine various classes of penetration enhancers, including 1-dodecylhexahydro-2H-azepin-2-one (Azone), oleic acid, propylene-glycol, menthol, ethoxyglycol-diethyleneglycol-monoethyl-ether (Transcutol), polysorbate-polyethylenesorbitan-monolaurate (Tween-20), and the drug 7-chloro-1-methyl-5-phenyl-3H-1,4-benzodiazepin-2-one (Diazepam). The assay enables to evaluate the validity of various observations and hypotheses proposed in previous studies regarding permeation enhancement activities. Our results suggest, for example. that propylene glycol (PG) by itself does not interfere with membranes, but rather exhibits synergistic effect in combination with other penetration enhancers. Similarly, our data demonstrate that Transcutol does not independently interact with membranes. The colorimetric system also indicates that interaction of penetration enhancers with membranes depend upon the lipid phase, as well as the self-assembly properties of the enhancer molecules. CONCLUSIONS: The new biomimetic model membrane system can be applied for rapid screening of the activities of penetration enhancers, and provides insight into the mechanisms of permeability of membrane-active compounds.

Acetylene↗
PubMed2000

Peptide-membrane interactions studied by a new phospholipid/polydiacetylene colorimetric vesicle assay.

Interactions between peptides and lipid membranes play major roles in numerous physiological processes, such as signaling, cytolysis, formation of ion channels, and cellular recognition. We describe a new colorimetric technique for studying peptide-membrane interactions. The new assay is based on supramolecular assemblies composed of phospholipids embedded in a matrix of polydiacetylene (PDA) molecules. The phospholipid/PDA vesicle solutions undergo visible color changes upon binding of membrane peptides. Experiments utilizing various analytical techniques confirm that the blue-to-red color transitions of the phospholipid/PDA vesicles are directly related to adoption of helical conformations by the peptides and their association with the lipids. Spectroscopic data indicate that the colorimetric transitions are correlated with important molecular parameters, such as the degree of penetration of the peptides into lipid bilayers, and the mechanisms of peptide-lipid binding. The results suggest that the new colorimetric assay could be utilized for studying interactions and organization of membrane peptides.

Acetylene↗
PubMed2000

A colorimetric assay for rapid screening of antimicrobial peptides.

The increased resistance of various bacteria toward available antibiotic drugs has initiated intensive research efforts into identifying new sources of antimicrobial substances. Short antibiotic peptides (10-30 residues) are prevalent in nature as part of the intrinsic defense mechanisms of most organisms and have been proposed as a blueprint for the design of novel antimicrobial agents. Antimicrobial peptides are generally believed to kill bacteria through membrane permeabilization and extensive pore-formation. Assays providing rapid and easy evaluation of interactions between antimicrobial membrane peptides and lipid bilayers could significantly improve screening for substances with effective antibacterial properties, as well as contribute to the elucidation of structural and functional properties of antimicrobial peptides. Here we describe a colorimetric sensor in which particles composed of phospholipids and polymerized polydiacetylene (PDA) lipids were shown to exhibit striking color changes upon interactions with antimicrobial membrane peptides. The color changes in the system occur because of the structural perturbation of the lipids following their interactions with antimicrobial peptides. The assay was also sensitive to the antibacterial properties of structurally and functionally related peptide analogs.

Acetylene↗
PubMed2000

Identification of heroin in street doses using 1D-TOCSY nuclear magnetic resonance

Heroin street doses are complex mixtures commonly analyzed in forensic laboratories. Identification of the illicit substance in these street doses is among the primary analytical tasks of a forensic laboratory. We demonstrate that the one-dimensional ID-TOCSY NMR experiment permits identification of heroin in standard mixtures containing up to ten or more different components. This method produces an easily-identified and effective "fingerprint" for heroin within a mixture of other substances. The method has been successfully tested as a tool for identification of heroin in street doses from police casework in Israel. This NMR technique is robust and quick (a measurement can be carried out in 10-15 min), and it does not require any preliminary physical or chemical treatments of the sample to be examined, due to the effective spectroscopic "filtering" of the interfering components. The ID-TOCSY NMR method can potentially be used in combination with additional analytical methods as a routine tool in forensic laboratories to positively identify heroin for court purposes.

Journal Article↗
PubMed1999

Effects of temperature and Y21M mutation on conformational heterogeneity of the major coat protein (pVIII) of filamentous bacteriophage fd.

Solid-state NMR spectroscopy was used to analyze the conformational heterogeneity of the major coat protein (pVIII) of filamentous bacteriophage fd. Both one and two-dimensional solid-state NMR spectra of magnetically aligned samples of fd bacteriophage reveal that an increase in temperature and a single site substitution (Tyr21 to Met, Y21M) reduce the conformational heterogeneity observed throughout wild-type pVIII. The NMR results are consistent with previous studies indicating that conformational flexibility in the hinge-bend segment that links the amphipathic and hydrophobic helices in the membrane-bound form of the protein plays an essential role during phage assembly, which involves a major change in the tertiary, but not secondary, structure of the coat protein.

Capsid↗
PubMed1998

Interfacial catalysis by phospholipases at conjugated lipid vesicles: colorimetric detection and NMR spectroscopy.

BACKGROUND: Self-assembled conjugated polymers are rapidly finding biological and biotechnological applications. This work describes a synthetic membrane system based on self-assembled polydiacetylenes, which are responsive to the enzymatic activity of phospholipases - a ubiquitous class of enzymes that catalyze the hydrolysis of phospholipid molecules embedded in cell membranes. RESULTS: We show that phospholipases are active at bilayer vesicles composed of the natural enzyme substrate, dimyristoylphosphatidylcholine (DMPC), and a synthetic pi-conjugated polymerized lipid based on polydiacetylene (PDA). In addition, the enzymatic reaction induces an optical transition in the surrounding PDA matrix, visible to the naked eye. Nuclear magnetic resonance spectroscopy confirms the occurrence of enzymatic catalysis and reveals the fate of the cleavage products. CONCLUSIONS: The results indicate that the structural and color changes of the PDA matrix are directly related to interfacial catalysis by phospholipase. This novel biocatalytic method of inducing optical transitions in conjugated polymers might lead to new approaches towards rapidly screening new enzyme inhibitor compounds.

Acetylene↗
PubMed1997

NMR structure of the principal neutralizing determinant of HIV-1 displayed in filamentous bacteriophage coat protein.

An NMR approach for structure determination of short peptides displayed on the surface of filamentous bacteriophage virions is demonstrated using the hexapeptide GPGRAF that constitutes the principal neutralizing determinant of HIV-1. This peptide was inserted near the N terminus of the major coat protein of bacteriophage fd. NMR studies of the recombinant protein solubilized in detergent micelles showed that the inserted peptide adopts a double bend S-shaped conformation that is similar to the antibody-bound structure determined by X-ray crystallography. This indicates that a peptide displayed on the bacteriophage coat protein has an enhanced propensity to adopt a conformation similar to that found in the native protein from which it is derived. This approach may be generally applicable to the structure determination of peptide epitopes and other small peptides.

Capsid↗
PubMed1995

Neurosecretory vesicles can be hybrids of synaptic vesicles and secretory granules.

We have investigated the relationship of the so-called small dense core vesicle (SDCV), the major catecholamine-containing neurosecretory vesicle of sympathetic neurons, to synaptic vesicles containing classic neurotransmitters and secretory granules containing neuropeptides. SDCVs contain membrane proteins characteristic of synaptic vesicles such as synaptophysin and synaptoporin. However, SDCVs also contain membrane proteins characteristic of certain secretory granules like the vesicular monoamine transporter and the membrane-bound form of dopamine beta-hydroxylase. In neurites of sympathetic neurons, synaptophysin and dopamine beta-hydroxylase are found in distinct vesicles, consistent with their transport from the trans-Golgi network to the site of SDCV formation in constitutive secretory vesicles and secretory granules, respectively. Hence, SDCVs constitute a distinct type of neurosecretory vesicle that is a hybrid of the synaptic vesicle and the secretory granule membranes and that originates from the contribution of both the constitutive and the regulated pathway of protein secretion.

Animals↗
PubMed1995

Synaptotagmin I- and II-deficient PC12 cells exhibit calcium-independent, depolarization-induced neurotransmitter release from synaptic-like microvesicles.

Synaptotagmin I- and II-deficient PC12 cells (Shoji-Kasai et al. [1]) were used to compare the role of this protein in the calcium-dependent exocytosis of secretory granules and synaptic-like microvesicles (SLMVs). While neither catecholamine nor protein secretion from secretory granules were altered, the depolarization-induced acetylcholine release from SLMVs was no longer calcium-dependent. We propose that within the exocytotic process of SLMVs, there exist two depolarization-induced steps. One is calcium-dependent and no longer present in synaptotagmin I- and II-deficient cells. The other is induced by depolarization, does not require calcium, and suffices to trigger neurotransmitter release from SLMVs in synaptotagmin I- and II-deficient PC12 cells.

Acetylcholine↗
PubMed1992

Solid-state 27Al NMR studies of aluminophosphate molecular sieves. Enhanced resolution by quadrupole nutation and double-rotation.

Solid-state 27Al NMR spectra of several aluminophosphate molecular sieves have been recorded with conventional magic-angle spinning (MAS), double-rotation (DOR) and quadrupole nutation with fast MAS. Enhanced resolution was obtained in the quadrupole nutation experiment at certain radiofrequency pulse strengths. This extra resolution can be comparable to that attainable using DOR, and does not introduce spinning sidebands.

Aluminum↗
PubMed1990

Impact of technology in health care and health administration: hospitals and alternative care delivery systems.

Applications as outlined above and many more that have not yet even been identified--but that will be invented and developed--will have an enormous impact on the health care industry. Clearly, capital requirements to purchase this technology will go up and thus exert further pressure for the reduction of personnel. Computers and robots will replace a significant percentage of health care personnel; overall health care costs as a percent of gross national product will nevertheless probably continue to rise in spite of improvements in productivity. Added costs will be offset in part by the use of technology in areas that will impact efficiency. Because of these accelerating uses of sophisticated technology, future administrators will have a greater appreciation for what technology can offer. Practical uses of robotics, expert systems, and artificial intelligence will require administrators to be technologically proficient.

Delivery of Health Care↗
PubMed1990

[Correlation of tumor site and tumor volume in radical surgery of cancer of the peripapillary area].

In a group of 52 partial duodenopancreatectomies (34 cancers of the head of the pancreas, 14 cancers of the papilla and 4 cancers of the common bile duct) the dependence of tumour volume and tumour localisation on carcinomatous lymph node involvement, infiltration of surrounding tissues, infiltration of great visceral vessels and not radical resection was determined. The analysis demonstrates that there is significant difference in volume between radically treated carcinomas of the common bile duct, the papilla of Vater and the head of the pancreas with mean volumes of 463:1,851:11,835 mm3 or 1:4:26! Furthermore the investigation shows that for every analysed parameter median volume is larger for positive observations than for negative ones: lymph node involvement 10,606:6,459 mm3, infiltration of surrounding tissues 10,444:6,703 mm3, infiltration of great visceral vessels 14,923:7,144 mm3, not radical resection 18,130:5,343 mm3. From these results it is concluded, that early stages of periampullary carcinomas with a good chance for cure are only present in radically treated cancers of the papilla and the common bile duct. In cancers of the head of the pancreas the significant larger primary cancers and the more advanced staging results in a dismal prognosis.

Ampulla of Vater↗
PubMed1989

[Change in the value of palliative interventions in cancer of the head of the pancreas].

An analysis of 412 patients with carcinoma of the head of the pancreas treated only with palliative procedures revealed remarkable differences in the results following internal anastomosis procedures and external T-tube drainage. The anastomosis group showed in comparing the years 1963-1982 with the years 1983-1987 a decline in the frequency of such procedures from 89% to 54% and a decline of the mortality from 12% to 4% while the survival time (220 days) showed no change. According to the low mortality rate we prefer internal anastomosis procedures to PTCD. However, as the results of T-tube drainage are still poor (mortality rate 36%; survival time 190 days) an attempt of PTCD seems indicated if the untreatable situation is recognized preoperative, as PTCD achieves similar results as T-tube drainage.

Aged↗
PubMed1988

Factors affecting mortality in transduodenal sphincteroplasty.

An analysis of 1,200 consecutive transduodenal sphincterotomies performed between 1967 and 1985 is presented herein. The over-all mortality rate was 3.75 per cent. Since 1980, however, the mortality rate has decreased to 2.1 per cent. The mortality rate was influenced by the age of the patient at the time of the operation (p less than 0.005). Furthermore, the mortality rate increased from decade to decade (less than 30 years, zero per cent; greater than 70 years, 6 per cent). The operative mortality rate was also influenced by general risk factors--hypertony (mortality rate of 5.8 per cent, not significant), diabetes (mortality rate of 6.5 per cent, p congruent to 0.05), renal failure (15.5 per cent, p less than 0.005), jaundice (bilirubin level in survivors, 78.3 micromoles per liter and in those who died, 120.4 micromoles per liter, p less than 0.005) and vital indication (mortality rate of 15 per cent, p less than 0.01). Although the indication for sphincterotomy had a small influence on the mortality (papilla stenosis without bile duct stones, 1.7 per cent; papilla stenosis with common duct stones, 3.6 per cent, and impacted stones in the papilla, 5.0 per cent), these small differences are not significant. A significant influence, however, was due to complicating intraoperative findings, such as bilioenteral fistulas (a mortality rate of 10.8 per cent, p less than 0.0005). The fact that the mortality rate increased in patients with T-tube insertion shows that operative problems and complications influence the mortality rate for sphincterotomy. From these results, we concluded that, in the aforementioned risk groups, a preoperative endoscopic sphincterotomy should be strongly considered, as the risk from the surgical procedure is diminished by the endoscopic relief of the obstruction of the biliary tract.

Adult↗
PubMed1987

[Eosinophilic gastroenteritis].

Eosinophilic gastroenteritis represents a very rare inflammatory disease of the stomach and bowel. Aetiologically an allergic diathesis must be assumed, but it is only very seldom that a particular allergen can be identified as being responsible for any case. Characterized by peripheral blood eosinophilia and eosinophilic infiltration of various parts of the gastro-intestinal tract, together with disturbed gastro-intestinal function, complications can arise in this disease requiring surgical intervention. In general, however, conservative therapy is adequate. The clinical features are discussed on the basis of an own case report.

Duodenum↗