Biomedical subjects

Laurel O Sillerud

Publications and source records attributed to Laurel O Sillerud.

6 recordsLinked to original sources

PubMed2006

1H NMR Detection of superparamagnetic nanoparticles at 1T using a microcoil and novel tuning circuit.

Magnetic beads containing superparamagnetic iron oxide nanoparticles (SPIONs) have been shown to measurably change the nuclear magnetic resonance (NMR) relaxation properties of nearby protons in aqueous solution at distances up to approximately 50 microm. Therefore, the NMR sensitivity for the in vitro detection of single cells or biomolecules labeled with magnetic beads will be maximized with microcoils of this dimension. We have constructed a prototype 550 microm diameter solenoidal microcoil using focused gallium ion milling of a gold/chromium layer. The NMR coil was brought to resonance by means of a novel auxiliary tuning circuit, and used to detect water with a spectral resolution of 2.5 Hz in a 1.04 T (44.2MHz) permanent magnet. The single-scan SNR for water was 137, for a 200 micros pi/2 pulse produced with an RF power of 0.25 mW. The nutation performance of the microcoil was sufficiently good so that the effects of magnetic beads on the relaxation characteristics of the surrounding water could be accurately measured. A solution of magnetic beads (Dynabeads MyOne Streptavidin) in deionized water at a concentration of 1000 beads per nL lowered the T(1) from 1.0 to 0.64 s and the T2 * from 110 to 0.91 ms. Lower concentrations (100 and 10 beads/nL) also resulted in measurable reductions in T2 *, suggesting that low-field, microcoil NMR detection using permanent magnets can serve as a high-sensitivity, miniaturizable detection mechanism for very low concentrations of magnetic beads in biological fluids.

Dextrans↗

PubMed2006

Citrate concentrations in human seminal fluid and expressed prostatic fluid determined via 1H nuclear magnetic resonance spectroscopy outperform prostate specific antigen in prostate cancer detection.

PURPOSE: We compared the performance of citrate concentration measurements in unprocessed human semen and expressed prostatic secretions from controls and from patients with biopsy confirmed prostate cancer to that of prostate specific antigen testing with respect to specificity and sensitivity for prostate cancer detection. MATERIALS AND METHODS: Semen and expressed prostatic secretions were collected in biopsy proven, prostate cancer bearing and noncancer bearing cases. Citrate concentrations were determined by quantitative in vitro, high field, water suppressed proton nuclear magnetic resonance spectroscopy. Assessments of the diagnostic performance of citrate and prostate specific antigen results in our study populations were made by ROC curve analysis. RESULTS: Citrate was measured in samples from 61 participants, of whom 16 without and 21 with cancer donated semen, and 17 without and 7 with cancer donated expressed prostatic secretions. Mean citrate +/- SE compared to that in controls was 2.7-fold lower in patients with cancer samples in semen (132.2 +/- 30.1 vs 48.0 +/- 7.9 mM, p < 0.05) and expressed prostatic secretions (221.4 +/- 55.4 vs 81.5 +/- 36.0 mM, p < 0.05). ROC curve analysis showed that measurements of citrate in semen performed as well as measurements of citrate in expressed prostatic secretion for detecting prostate cancer (AUC 0.81, 95% CI 0.60 to 0.92 and AUC 0.73, 95% CI 0.38 to 0.90, respectively, p > 0.05). ROC curve analysis also showed that the measurement of citrate in either fluid outperformed prostate specific antigen measurement for detecting prostate cancer in these subjects (AUC 0.61, 95% CI 0.44 to 0.74). CONCLUSIONS: In vitro nuclear magnetic resonance spectroscopic measurement of the citrate concentration in semen or expressed prostatic secretions outperforms prostate specific antigen testing for detecting prostate cancer.

Aged↗

PubMed2006

Nuclear magnetic resonance-based screening methods for drug discovery.

Nuclear magnetic resonance (NMR) techniques are widely used in the drug discovery process. The primary feature exploited in these investigations is the large difference in mass between drugs and receptors (usually proteins) and the effect that this has on the rotational or translational correlation times for drugs bound to their targets. Many NMR parameters, such as the diffusion coefficient, spin diffusion, nuclear Overhauser enhancement, and transverse and longitudinal relaxation times, are strong functions of either the overall tumbling or translation of molecules in solution. This has led to the development of a wide variety of NMR techniques applicable to the elucidation of protein and nucleic acid structure in solution, the screening of drug candidates for binding to a target of choice, and the study of the conformational changes that occur in a target on drug binding. High-throughput screening by NMR methods has recently received a boost from the introduction of sophisticated computational techniques for reducing the time needed for the acquistion of the primary NMR data for multidimensional studies.

Binding Sites↗

PubMed2005

A decrease in 1H nuclear magnetic resonance spectroscopically determined citrate in human seminal fluid accompanies the development of prostate adenocarcinoma.

PURPOSE: Because human prostatic fluid contributes almost 50% of the volume of seminal plasma and this fluid contains unique prostatic metabolites such as citrate, which are markedly altered during tumorigenesis, we investigated high resolution H nuclear magnetic resonance (NMR) spectroscopy of unprocessed human seminal plasma as a rapid, noninvasive diagnostic tool for prostate adenocarcinoma. MATERIALS AND METHODS: Semen and prostatic massage samples from control and tumor bearing subjects were stored frozen at -20C and thawed prior to water suppressed NMR analysis. We found that freezing produced no significant alterations in the semen NMR spectra. Quantitative NMR spectroscopy was performed by first calibrating the water suppression data acquisition sequence with a series of standard samples containing known amounts of citrate within the physiological range. RESULTS: Well resolved citrate resonances from the seminal plasma of 3 control subjects with prostate specific antigen (PSA) less than 1 ng/ml were integrated to give concentrations of 97 to 178 mM. Semen from a 47-year-old man with benign prostatic hyperplasia and a PSA of 5.5 ng/ml contained 156 mM citrate. In contrast, seminal plasma from 2 patients with prostate cancer, including a 46-year-old man with Gleason grade 8 and PSA 45.2 ng/ml, and a 64-year-old man with grade 6 and PSA 13.0 ng/ml, revealed citrate NMR signals corresponding to a concentration of only 28 and 24 mM, respectively. Spectra from prostatic massage fluid from a normal 23-year-old volunteer showed a citrate of 483 mM, while massage fluid from a 56-year-old patient with Gleason grade 4 cancer showed a citrate of only 1.35 mM. CONCLUSIONS: To our knowledge this study is the first to use high resolution NMR of semen to diagnose prostate cancer. Given the known effects of adenocarcinoma on prostate metabolism, the study indicates that high resolution H NMR can be used to measure citrate in seminal fluid, potentially providing a new, rapid, noninvasive screening method.

Adenocarcinoma↗

PubMed2005

Design and structure of peptide and peptidomimetic antagonists of protein-protein interaction.

Peptides based on the amino acid sequences found at protein-protein interaction sites make excellent leads for antagonist development. A statistical picture of amino acids involved in protein-protein interactions indicates that proteins recognize and interact with one another through the restricted set of specialized interface amino acid residues, Pro, Ile, Tyr, Trp, Asp and Arg. These amino acids represent residues from each of the three classes of amino acids, hydrophobic, aromatic and charged, with one anionic and one cationic residue at neutral pH. The use of peptides as drug leads has been successfully used to search for antagonists of cell-surface receptors. Peptide, peptidomimetic, and non-peptide organic inhibitors of a class of cell surface receptors, the integrins, currently serve as therapeutic and diagnostic imaging agents. In this review, we discuss the structural features of protein-protein interactions as well as the design of peptides, peptidomimetics, and small organic molecules for the inhibition of protein-protein interactions. Information gained from studying inhibitors of integrin functions is now being applied to the design and testing of inhibitors of other protein-protein interactions. Most drug development progress in the past several decades has been made using the enzyme binding-pocket model of drug targets. Small molecules are designed to fit into the substrate-binding pockets of proteins based on a lock-and-key, induced-fit, or conformational ensemble model of the protein binding site. Traditionally, enzymes have been used as therapeutic drug targets because it was easier to develop rapid, sensitive screening assays, and to find low molecular weight inhibitors that blocked the active site. However, for proteins which interact with other proteins, rather than with small substrate molecules, the lack of binding pockets means that this approach will not generally succeed. There exist many diseases in which the inhibition of protein-protein interactions would provide therapeutic benefit, but there are no general methods available to address such problems. The focus of the first part of this review is to discuss the features of protein-protein interactions which may serve as general guidelines for the development and design of inhibitors for protein-protein interactions. In the second part we focus on the design of peptides (lead compounds) and their conversion into peptidomimetics or small organic molecules for the inhibition of protein-protein interactions. We draw examples from the important and emerging area of integrin-based cell adhesion and show how the principles of protein-protein interactions are followed in the discovery, optimization and usage of specific protein interface peptides as drug leads.

Amino Acids↗

PubMed2004

The signature molecular descriptor. 3. Inverse-quantitative structure-activity relationship of ICAM-1 inhibitory peptides.

We present a methodology for solving the inverse-quantitative structure-activity relationship (QSAR) problem using the molecular descriptor called signature. This methodology is detailed in four parts. First, we create a QSAR equation that correlates the occurrence of a signature to the activity values using a stepwise multilinear regression technique. Second, we construct constraint equations, specifically the graphicality and consistency equations, which facilitate the reconstruction of the solution compounds directly from the signatures. Third, we solve the set of constraint equations, which are both linear and Diophantine in nature. Last, we reconstruct and enumerate the solution molecules and calculate their activity values from the QSAR equation. We apply this inverse-QSAR method to a small set of LFA-1/ICAM-1 peptide inhibitors to assist in the search and design of more-potent inhibitory compounds. Many novel inhibitors were predicted, a number of which are predicted to be more potent than the strongest inhibitor in the training set. Two of the more potent inhibitors were synthesized and tested in-vivo, confirming them to be the strongest inhibiting peptides to date. Some of these compounds can be recycled to train a new QSAR and develop a more focused library of lead compounds.

Drug Design↗