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L W Jelinski

Publications and source records attributed to L W Jelinski.

At least 19 recordsLinked to original sources
PubMed1998

Rotational-echo double-resonance in complex biopolymers: a study of Nephila clavipes dragline silk.

Rotational-Echo Double-Resonance (REDOR) NMR on strategically 13C and 15N labeled samples is used to study the conformation of the LGXQ (X = S, G, or N) motif in the major ampullate gland dragline silk from the spider Nephila clavipes. A method is described for calculating REDOR dephasing curves suitable for background subtractions, using probability distributions of nitrogen atoms surrounding a given carbon site, which are developed from coordinates in the Brookhaven Protein Data Bank. The validity of the method is established by comparison to dephasings observed from natural abundance 13C peaks for G and A. Straightforward fitting of universal REDOR dephasing curves to the background corrected peaks of interest provides results which are not self-consistent, and a more sophisticated analysis is developed which better accounts for 15N labels which have scrambled from the intended positions. While there is likely some heterogeneity in the structures formed by the LGXQ sequences, the data indicate that they all form compact turn-like structures.

Amino Acid Sequence↗
PubMed1996

Molecular orientation and two-component nature of the crystalline fraction of spider dragline silk.

The molecular origin of the exceptional mechanical properties of spider silk is unclear. This paper presents solid-state 2H nuclear magnetic resonance data from unoriented, oriented, and supercontracted fibers, indicating that the crystalline fraction of dragline silk consists of two types of alanine-rich regions, one that is highly oriented and one that is poorly oriented and less densely packed. A new model for the molecular-level structure of individual silk molecules and their arrangement in the fibers is proposed. These data suggest that it will be necessary to control the secondary structure of individual polymer molecules in order to obtain optimum properties in bio-inspired polymers.

Alanine↗
PubMed1996

13C NMR of Nephila clavipes major ampullate silk gland.

The major ampullate glands of the spider Nephila clavipes contain approximately 0.2 microliter each of a highly concentrated (approximately 50%) solution of silk fibroin. Therefore, the reservoir of silk in these glands presents an ideal opportunity to observe prefolded conformations of a protein in its native state. To this end, the structure and conformation of major ampullate gland silk fibroin within the glands of the spider N. clavipes were examined by 13C NMR spectroscopy. These results were compared to those from silk protein first drawn from the spinneret and then denatured. The 13C NMR chemical shifts, along with infrared and circular dichroism data, suggest that the silk fibroin in the glands exists in dynamically averaged helical conformations. Furthermore, there is no evidence of proline residues in U-(13)C-D-glucose-labeled silk. This transient prefolded "molten fibril" state may correspond to the silk I form found in Bombyx mori silk. There is no evidence of the final beta-sheet structure in the ampullate gland silk fibroin before final silk processing. However, the conformation of silk in the glands appears to be in a highly metastable state, as plasticization with water produces the beta-sheet structure. Therefore, the ducts connecting the ampullate glands to the spinnerets play a larger role in silk processing than previously thought.

Alanine↗
PubMed1996

Presence of phosphorus in Nephila clavipes dragline silk.

Solid-state 31P-NMR of Nephila clavipes dragline silk indicates the presence of phosphorus in at least two chemically distinct environments. Amino acid analyses of acid-hydrolyzed silk confirm the presence of phosphotyrosine as one of the phosphorus-containing components. The unusual chemical shift (18.9 ppm downfield from 85% H3PO4), proton chemical shift, and acid lability of a second component suggest that it is part of a strained five-membered cyclic phosphate that might be found on a beta-D-ribose. The five-membered cyclic phosphate is not removed from the silk fibers by exhaustive aqueous extraction. It is absent in nascent silk fibroin from the glands, suggesting that its formation is part of the fiber processing that occurs in the ducts leading to the spinnerets. High-resolution NMR spectra of silk dissolved in propionic acid/12 N HCl (50:50 v/v) show five phosphorus sites assigned to phosphorylated tyrosine residues, phosphorylated serine residues, inorganic phosphate, and two hydrolysis products of the cyclic phosphate compound. The observed posttranslational phosphorylation may be important in the processing and modulation of the physical properties of dragline silk.

Animals↗
PubMed1995

Self-diffusion monitors degraded cartilage.

This article demonstrates that both the bulk water self-diffusion coefficient (D) and the spatially resolved variation in D for lesion canine cartilage due to osteoarthritis is increased by about 25% over that of surrounding cartilage. This increase in D can be mimicked by enzymatic degradation of cartilage with trypsin, hyaluronidase, and collagenase, or by mechanical means. However, it is established here using excised disks of living cartilage whose proteoglycan and collagen contents were manipulated by biochemical intervention in tissue culture that the diffusion measurement is not sensitive to the proteoglycan content of cartilage. Instead, self-diffusion appears to monitor mesoscopic (nonspecific) tissue damage. These results show that D, measured in a spatially resolved manner by pulsed field gradient nuclear magnetic resonance imaging, can localize regions of cartilage degradation.

Animals↗
PubMed1994

Diffusion and relaxation mapping of cartilage-bone plugs and excised disks using microscopic magnetic resonance imaging.

Spatially resolved maps of proton self-diffusion coefficients (D) and relaxation times (T1 and T2) were obtained on cartilage-bone plug samples and on excised disks of canine cartilage at a transverse resolution of 30 microns, using microscopic magnetic resonance imaging (micro-MRI). Results are compared for excised disks of cartilage and intact cartilage-bone plugs. Correlations between the absolute water concentration, the self-diffusion coefficient and the T1 relaxation are reported. The diffusion coefficient is not a linear function of water concentration. The thickness of the disks is 600 microns, compared with the ca. 900 microns observed for the cartilage-bone plugs, presumably due to the absence of the interfacial or tidemark layer of interdigitated cartilage and bone in the former samples. Our results suggest that excised disks of cartilage are excellent models for the articular surface and the first 500 or so microns of tissue. The molecular parameters of spin-spin and spin-lattice relaxation times, as well as the water self-diffusion coefficient, are virtually identical in the two types of samples. However, the cartilage-bone plugs have the additional feature of permitting the study of the tidemark region, a region that likely plays a major role in the transmission of mechanical force.

Animals↗
PubMed1993

Oscillatory flow in the cochlea visualized by a magnetic resonance imaging technique.

We report a magnetic resonance imaging technique that directly measures motion of cochlear fluids. It uses oscillating magnetic field gradients phase-locked to an external stimulus to selectively visualize and quantify oscillatory fluid motion. It is not invasive, and it does not require optical line-of-sight access to the inner ear. It permits the detection of displacements far smaller than the spatial resolution. The method is demonstrated on a phantom and on living rats. It is projected to have applications for auditory research, for the visualization of vocal tract dynamics during speech and singing, and for determination of the spatial distribution of mechanical relaxations in materials.

Animals↗
PubMed1992

Industrial ecology: concepts and approaches.

Industrial ecology is a new approach to the industrial design of products and processes and the implementation of sustainable manufacturing strategies. It is a concept in which an industrial system is viewed not in isolation from its surrounding systems but in concert with them. Industrial ecology seeks to optimize the total materials cycle from virgin material to finished material, to component, to product, to waste product, and to ultimate disposal. To better characterize the topic, the National Academy of Sciences convened a colloquium from which were derived a number of salient contributions. This paper sets the stage for the contributions that follow and discusses how each fits into the framework of industrial ecology.

Journal Article↗
PubMed1990

Importance of the membrane in ligand-receptor interactions.

NMR data that underscore the importance of the membrane in ligand-receptor interactions were obtained and analyzed. The following hypothesis for acetylcholine (ACh) binding to the acetylcholine receptor (AChR) is proposed: ACh first binds to the membrane, where it adopts its bioactive conformation, and it then rapidly diffuses along the membrane to bind to the AChR in its already-correct conformation. Data used to support this hypothesis include (a) the NMR-determined binding constant of KM = (2.8 +/- 0.6) x 10(3) M-1 for the binding of ACh to the asolectin membrane, (b) the lipid dependence of AChR activity, (c) the location of the ACh binding site close to the membrane surface, and (d) the conformation of ACh in its membrane-bound state. Additional experiments to test this hypothesis are proposed.

Acetylcholine↗
PubMed1990

Stroboscopic nuclear magnetic resonance microscopy of arterial blood flow.

NMR microscopy was used to obtain transverse flow profiles of arterial blood flow in the rat carotid artery at 33 microns resolution. The images were gated to the EKG and correspond to identified regions of diastole. The profiles show that flow is laminar during this part of the heart cycle. These results provide the first direct view of blood flow profiles in arteries of submillimeter diameter and suggest that animals as small as juvenile rodents will serve as valuable models for hemodynamic studies. Extensions to flow during systole, stenoses, and flow in the vicinity of the carotid bifurcation are discussed.

Animals↗
PubMed1989

Stroboscopic NMR microscopy of the carotid artery.

The non-invasive measurement of vascular dynamics and elasticity is critical in understanding haemodynamic conditions of cardiovascular diseases such as hypertension and atherosclerosis. Although there are numerous invasive and in vitro techniques for such measurements, until now non-invasive methods have been limited. We have now obtained stroboscopic NMR images of the carotid arteries of 80-g rats. The change in the cross-sectional area of arteries of diameter approximately 600-800 microns was correlated with the change in absolute blood pressure. These are the first microimages of a dynamic system and enable the direct visualization of compliance, the non-invasive measurement of Young's modulus, the direct determination of the local effects of vasoconstrictors and vasodilators and the mapping of the entire cardiac cycle.

Animals↗
PubMed1988

Measuring relative acetylcholine receptor agonist binding by selective proton nuclear magnetic resonance relaxation experiments.

A method is presented that uses selective proton Nuclear Magnetic Resonance (NMR) relaxation measurements of nicotine in the presence of the acetylcholine receptor to obtain relative binding constants for acetylcholine, carbamylcholine, and muscarine. For receptors from Torpedo californica the results show that (a) the binding constants are in the order acetylcholine greater than nicotine greater than carbamylcholine greater than muscarine; (b) selective NMR measurements provide a rapid and direct method for monitoring both the specific and nonspecific binding of agonists to these receptors and to the lipid; (c) alpha-bungarotoxin can be used to distinguish between specific and nonspecific binding to the receptor; (d) the receptor--substrate interaction causes a large change in the selective relaxation time of the agonists even at concentrations 100x greater than that of the receptor. This last observation means that these measurements provide a rapid method to monitor drug binding when only small amounts of receptor are available. Furthermore, the binding strategies presented here may be useful for the NMR determination of the conformation of the ligand in its bound state.

Acetylcholine↗
PubMed1988

Conformation of acetylcholine bound to the nicotinic acetylcholine receptor.

We report here the biologically active conformation of acetylcholine when bound to the high-affinity state of the receptor from Torpedo californica. The acetylcholine conformation was determined in the free and bound states by proton NMR two-dimensional nuclear Overhauser effects. In agreement with x-ray crystallographic data, acetylcholine in solution has an extended conformation with an average distance between the acetyl methyl and choline methyl protons of approximately equal to 5 A. When bound to the acetylcholine receptor, acetylcholine adopts a conformation where the acetyl methyl group is close (3.3 A) to the methyl groups of the choline moiety. This bent conformation places the oxygens adjacent to one another and allows the methyl groups to form an uninterrupted hydrophobic surface over the rest of the acetylcholine molecule. The significant difference between the free- and bound-state conformations implies that structure-activity studies based solely on molecular modeling strategies must be approached with caution.

Acetylcholine↗
PubMed1985

Combining solid-state and solution-state 31P NMR to study in vivo phosphorus metabolism.

Otherwise unavailable information concerning the distribution of phosphorylated compounds in biological systems is obtained by a combined solid-state/solution-state NMR approach, illustrated here for oocytes from Rana pipiens. General methodology is developed, and further extensions are proposed. The following conclusions pertain to the specific system under examination. (i) Nucleoside phosphates can be observed by magic-angle sample spinning of the lyophilized material. (ii) The solid-state NMR technique of dipolar decoupling provides no additional resolution of the phospholipid and phosphoprotein components of the yolk. However, cellular death produces sufficient pH changes to cause the phospholipid and protein phosphate peaks to become resolvable. The concentration of nucleoside phosphates also decreases. (iii) The phospholipid and phosphoprotein components are shown by computer simulation to be present in a ratio of 40:60, respectively. (iv) The amounts of inorganic phosphate, nucleoside phosphates, and sugar phosphates are determined by solution-state NMR observation of the perchloric acid extract of the oocytes.

Animals↗
PubMed1983

Mobility and function in elastin and collagen.

13C- and 2H-labelled amino acids have been incorporated into elastin and collagen and rotational correlation times of the labelled sites have been derived from an analysis of nuclear magnetic resonance relaxation parameters and line-shapes. The elastin experiments were designed to discriminate between the various models that have been proposed to account for the rubber-like elasticity of elastin. The correlation times of carbonyl carbons of the elastin backbone show that elastin chains are very flexible at the molecular level. In addition, the molecular dynamics and viscoelastic behaviour of elastin are well correlated over a wide range of temperatures and solvents. These results all support the rubber-like network model of elastin structure. The collagen experiments were designed to investigate the intermolecular interactions between molecules in collagen fibres. Correlation times of labelled sites in the collagen backbone and side-chains show that substantial flexibility, especially of the side-chains, takes place in reconstituted (non-cross-linked) collagen fibrils. Therefore, the interactions between side-chains that presumably direct and stabilize the fibrillar assembly take place in fluid domains. The molecular flexibility is not affected by the presence of cross-links but is absent when the collagen is mineralized.

Animals↗
PubMed1982

Characterization of leucine side-chain reorientation in collagen-fibrils by solid-state 2H NMR.

We have used 2H quadrupole-echo NMR spectroscopy to study the molecular dynamics of the leucine side chain in collagen fibrils labeled with [2H10]leucine. X-ray crystallographic studies of leucine and small leucyl-containing peptides and proteins [Benedetti, C. (1977) in Proceedings of the Fifth American Peptides Symposium, eds, Goodman, M. & Meienhofer, J. (Wiley, New York), pp. 257--274; Janin, J., Wodak, S., Levitt, M. & Maigret, B. (1978) J. Mol. Biol. 125, 357--386] show that the amino acid side chain exists predominantly in only two of the nine possible conformations. 2H NMR spectra of polycrystalline D,L [2H10]leucine obtained from -45 degrees C to +100 degrees C showed that interconversion of the two conformations did not take place on the 2H NMR timescale in this temperature range. In contrast, experimental lineshapes observed for [2H10]leucine-labeled collagen fibrils from -85 degrees C to +30 degrees C were simulated by using a model in which the side chain hops at various rates between the two predominant conformations found by the x-ray studies. A small difference between calculated and observed linewidths above the freezing point of water can be accounted for by backbone reorientation or by the presence of a small percentage of other side-chain conformations. Thus, these results provide strong evidence that the two predominant x-ray conformations not only exist in the fibrils as the preferred orientations but interconvert at rates that are proportional to temperature over the range - 85 degrees C to +30 degrees C. These observations concur with previous NNR studies of collagen fibrils that demonstrated a mobile contact region between collagen molecules.

Animals↗
PubMed1980

2H NMR study of molecular motion in collagen fibrils.

Collagen was labelled through tissue culture with [3,3,3-d3]alanine. 2HNMR spectra were obtained of the labelled collagen as fibrils and in solution using the quadrupolar echo technique for solids. The 2H NMR data were analysed in terms of a model for reorientation in which the molecule is considered to jump between two orientations in a time which is short compared to the residence time in each site, and short compared to (delta vq)-1. The best fit of the data indicates that the collagen molecule in the fibrils experiences reorientation about its long axis over an angular range of approximately 30--40 degrees. The T2 for [3,3,3-d3]alanine-labelled collagen fibrils is estimated to be approximately 110 mus.

Alanine↗