Papers by Peter Bergethon
The Physical Basis of Biochemistry, 2010
The Journal of Physical Chemistry B, 2013
Environment polarity can cause changes in absorbance or emission maxima, for a given fluorophore.... more Environment polarity can cause changes in absorbance or emission maxima, for a given fluorophore. This is termed solvatochromism. In this study semiempirical models of solvatochromic shifts are used to predict their lipid bilayer location. Four reaction field models are analyzed and compared, to provide the most accurate prediction of fluorophore solvatochromic shifts using a modified version of the Lippert equation. For curcumin, the reaction field of Block and Walker gave the strongest agreement between experimental and predicted values (r = 0.978, p < 0.0001). For aluminum phthalocyanine disulfonic acid (AlPcS2), the reaction field of Wertheim, based on statistical mechanics, gave the best agreement (r = 0.951, p = 0.001) only when dispersion forces and solute polarizability are considered. The results of these models are correlated to the Dimroth-Reichardt ET(30) solvent polarity scale used by Frimer and colleagues. Using the model predicted values, curcumin is estimated to be 1-1.2 nm from the phospholipid-water interface, in the acyl chain region of the lipid bilayer. AlPcS2 is predicted to be 0.7-0.9 nm from the interface, at the fatty acid carbonyl. This investigation provides semiempirical methods to efficiently link fluorophore solvatochromic shifts to a location in the lipid bilayer via reaction field models.
Journal of Chemical Information and Modeling, 1997
Biophysical Journal, 1991
The flow of the blood past the vascular wall gives rise to an electrical potential. This field is... more The flow of the blood past the vascular wall gives rise to an electrical potential. This field is calculated to have a periodic waveform with a transluminal peak-to-peak amplitude of -1.35 V/m-1. Digital imaging fluorescent microscopy was used to measure changes in the membrane potentials of smooth muscle cells by following changes in the fluorescence of the potential sensitive dye, 3,3'-dipropyloxacarbocyanine iodide (di-O-C5[3]). The effect of the low level electrical field on the membrane potentials of cultured smooth muscle vascular cells was shown to cause a steady-state depolarization of 10 mV. The degree of steady-state depolarization was shown to directly vary with the frequency of the applied field and the effect was not dependent on the presence of extracellular Ca+2 or Mg+2. These effects are thought to be most consistent with an electroconformational coupling mechanism. The presence of this electrokinetic field was also shown to alter the electrophysiological response of smooth muscle cells treated with 5-hydroxytryptamine. Cells exposed concurrently to both 5-HT and the electrical field showed an increased membrane depolarization thus implying that the electrokinetic field may be important in both normal and pathologic cellular responses. 588 0006-3495/91/09/588/08 $2.00
Biophysical Journal, 2013
Lipid-linked oligosaccharides (LLO) are intermediates in glycosylation in prokaryotes and eukaryo... more Lipid-linked oligosaccharides (LLO) are intermediates in glycosylation in prokaryotes and eukaryotes. An LLO is composed of a lipid molecule joined by diphosphate to a sugar chain. However, the structure, dynamics, and orientation (with respect to bilayers) of LLO within biological membranes have not been explored previously. Using the recent CHARMM carbohydrate and general force fields, we have constructed two types of LLO: one based on the lipid molecule dolichol (DOL), which is found ubiquitously in eukaryotes, and one based on undecaprenol (UND), which is found in bacteria. We have simulated each LLO type in four different pure bilayer types with different hydrophobic thicknesses and saturations: DLPC (dilauroylphosphatidylcholine), DMPC (dimyristoylphosphatidylcholine), DOPC (dioleoylphosphatidylcholine), and SAPC (stearoylarachidonylcholine). The simulation results of each system will be discussed in terms of density distribution of each component along the membrane normal, RMSD and RMSF of oligosaccharides, oligosaccharides' conformations, DOL and UND conformations, orientations of oligosaccharides with respect to the bilayer normal, and interactions of oligosaccharide with the bilayer.
The Physical Basis of Biochemistry, 2010
We have constructed a view of biochemical state space based predominantly on the ideas of a limit... more We have constructed a view of biochemical state space based predominantly on the ideas of a limited set of mechanical motions and the existence of electrical charge. Using just these basic concepts we have been able to develop useful descriptions of light and electromagnetic radiation and subsequently of atomic and molecular structure. These ideas are developed from the same core physical concepts. Therefore it is not surprising that a substantial interaction between electromagnetic radiation and matter will be found. A great deal of structural information can be gained by studying these interactions. In general we can explore structure of biological molecules by either focusing on either the quantum mechanical aspects or the wave-like nature of light. The first forms the basis of spectroscopic experimental methods and is the subject of this chapter and the second, the basis of light scattering (e.g., x-ray diffraction) and is the subject of Chapter 29.
The Physical Basis of Biochemistry, 2010
The Physical Basis of Biochemistry, 2010
Conversions
The Physical Basis of Biochemistry, 1998
Angiology, 2013
Small vessel (SV) and large vessel (LV) brain infarcts are distinct pathologies. Using a homeboun... more Small vessel (SV) and large vessel (LV) brain infarcts are distinct pathologies. Using a homebound elderly sample, the numbers of either infarct subtypes were similar between those apolipoprotein E4 allele (ApoE4) carriers (n = 80) and noncarriers (n = 243). We found that the higher the number of SV infarcts, but not LV infarcts, a participant had, the higher the activity of substrate V degradation in serum especially among ApoE4 carriers (β = +0.154, SE = 0.031, P < .0001) after adjusting for the confounders. Since substrate V degradation could be mediated by insulin-degrading enzyme (IDE) or/and angiotensin-converting enzyme (ACE), but no relationship was found between SV infarcts and specific ACE activities, blood IDE may be a useful biomarker to distinguish the brain infarct subtypes. Insulin-degrading enzyme in blood may also imply an important biomarker and a pathological event in Alzheimer disease through SV infarcts in the presence of ApoE4.
Biophysical Chemistry, 1990
Journal of Cell Science
The interactions between cells and their extracellular substratum environment are complex and dif... more The interactions between cells and their extracellular substratum environment are complex and difficult to study. Defined, synthetic substrata are valuable tools for experimentally determining the role of ionic and receptor-specific interactions between cells and their substrata. Hydrogels have been modified to contain stoichiometrically defined quantities of both positive and negative charge as well as specific proteins. These synthetic surfaces are water-rich matrices that possess hydroxyl groups, positive and negative ionized charges and native proteins, and can be considered as models of extracellular matrices on which an assessment of charge contribution and macromolecular content and specificity can be addressed with respect to cell-matrix interactions. This study shows that simple gels made of polyhydroxyethylmethacrylate do not support the spreading of cells but that the generation of copolymers by the addition of monomers that contain ionizable functional groups, will permi...
The Physical Basis of Biochemistry, 2010
The Physical Basis of Biochemistry, 2010
The Physical Basis of Biochemistry, 1998
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Papers by Peter Bergethon