Bulk and interfacial properties of binary hard-platelet fluids

Interfaces between demixed fluid phases of binary mixtures of hard platelets are investigated using density-functional theory. The corresponding excess free energy functional is calculated within a fundamental measure theory adapted to the Zwanzig model, in which the orientations of the particles of rectangular shape are restricted to three orthogonal orientations. Density and orientational order parameter profiles at interfaces between coexisting phases as well as the interfacial tension are determined. A density inversion, oscillatory density profiles, and a Fisher-Widom line have been found in a mixture of large thin and small thick platelets. The lowest interfacial tension corresponds to the mean bulk orientation of the platelets being parallel to the interface. For a mixture of large and small thin platelets, complete wetting of an isotropic-nematic interface by a second nematic phase is found.

Kinetics of sealing for transient electropores in isolated mammalian skeletal muscle cells

Permeabilization of the plasma membrane by electrical forces (electroporation) can be either transient or stable. Although the exact molecular mechanics have not yet been described, electroporation is believed to initiate primarily in the lipid bilayer. To better understand the kinetics of membrane permeabilization, we sought to determine the time constants for spontaneous transient pore sealing. By using isolated rat flexor digitorum brevis skeletal muscle cells and a two-compartment diffusion model, we found that pore sealing times (tau p) after transient electroporation were approximately 9 min. tau p was not significantly dependent on the imposed transmembrane potential. We also determined the transmembrane potential (delta Vm) thresholds necessary for transient and stable electroporation in the skeletal muscle cells. delta VmS ranging between 340 mV and 480 mV caused a transient influx of magnesium, indicating the existence of spontaneously sealing pores. An imposed delta Vm of 540 mV or greater led to complete equilibration of the intracellular and extracellular magnesium concentrations. This finding suggests that stable pores are created by the larger imposed transmembrane potentials. These results may be useful for understanding nerve and skeletal muscle injury after an electrical shock and for developing optimal strategies for accomplishing transient electroporation, particularly for gene transfection and cell transformation.

Nonlinearly coupled flows

We study energy flows that are coupled at a higher than linear order. A number of examples are presented where a force brings about a flow in the perpendicular direction. In some cases the symmetry of the system is such that coupling can only take place at even orders. We apply the theory to recently proposed two-dimensional devices that separate colloidal particles by ratcheting the different particles in different directions.

Association of yeast RNA polymerase I with a nucleolar substructure active in rRNA synthesis and processing

A novel ribonucleoprotein complex enriched in nucleolar proteins was purified from yeast extracts and constituents were identified by mass spectrometry. When isolated from rapidly growing cells, the assembly contained ribonucleic acid (RNA) polymerase (pol) I, and some of its transcription factors like TATA-binding protein (TBP), Rrn3p, Rrn5p, Rrn7p, and Reb1p along with rRNA processing factors, like Nop1p, Cbf5p, Nhp2p, and Rrp5p. The small nucleolar RNAs (snoRNAs) U3, U14, and MRP were also found to be associated with the complex, which supports accurate transcription, termination, and pseudouridylation of rRNA. Formation of the complex did not depend on pol I, and the complex could efficiently recruit exogenous pol I into active ribosomal DNA (rDNA) transcription units. Visualization of the complex by electron microscopy and immunogold labeling revealed a characteristic cluster-forming network of nonuniform size containing nucleolar proteins like Nop1p and Fpr3p and attached pol I. Our results support the idea that a functional nucleolar subdomain formed independently of the state of rDNA transcription may serve as a scaffold for coordinated rRNA synthesis and processing.

How yeast cells synchronize their glycolytic oscillations: a perturbation analytic treatment

Of all the lifeforms that obtain their energy from glycolysis, yeast cells are among the most basic. Under certain conditions the concentrations of the glycolytic intermediates in yeast cells can oscillate. Individual yeast cells in a suspension can synchronize their oscillations to get in phase with each other. Although the glycolytic oscillations originate in the upper part of the glycolytic chain, the signaling agent in this synchronization appears to be acetaldehyde, a membrane-permeating metabolite at the bottom of the anaerobic part of the glycolytic chain. Here we address the issue of how a metabolite remote from the pacemaking origin of the oscillation may nevertheless control the synchronization. We present a quantitative model for glycolytic oscillations and their synchronization in terms of chemical kinetics. We show that, in essence, the common acetaldehyde concentration can be modeled as a small perturbation on the "pacemaker" whose effect on the period of the oscillations of cells in the same suspension is indeed such that a synchronization develops.

Intrawell relaxation of overdamped Brownian particles

We consider an overdamped Brownian particle in a well. When the particle escapes, it does so as an instanton, i.e., in one run and without dwelling anywhere on the way from the bottom of the well to the top of the barrier. For a sufficiently steep slope the instanton time equals the time it takes the particle to deterministically slide down the same slope. We show that the instanton time is also the relaxation time for the escape rate after the barrier changes shape.

Recycling isoelectric focusing and isotachophoresis

Of all electrophoretic methods, isoelectric focusing offers the highest resolution and is best suited for preparative applications. Over the years, several instruments were developed for this purpose, all operating in free fluids, in the absence of gels or other supporting matrices. In such systems, the avoidance of gravity or electrically driven convections is essential. Successful stratagems for fluid control included rapid recycling or rotation, in combination with either fine porosity screens or narrow gaps between parallel plates. The most successful apparatus so far is the Rotofor, in which fluid is stabilized by combining horizontal rotation with fine porosity screen partitioning. Recycling isotachophoresis offers the potential of separating proteins at high concentration. A new concept of tangential electrophoresis is described. To optimize the use of these devices for protein separation, low molecular weight, biologically acceptable buffers of known composition are essential. The buffering system developed for this purpose comprises a series of binary buffers that cover the pH range in steps of 1 pH unit or less. The pH gradient can be custom-designed and is of remarkable stability in operation.

Alteration in sensory nerve function following electrical shock

A study of the effects of electrical shock on peripheral nerve fibres is presented. Strength and duration of the applied shocks were similar to those encountered in a typical industrial electrical accident. The purpose of this study is: (i) to identify the electrophysiological and morphological change in nerve fibres after the application of electrical current shocks; (ii) to examine the ability of the peripheral nerve fibres to spontaneously regain function and; (iii) to demonstrate the usefulness of the sensory refractory spectrum as an additional technique in assessing the damage. Three groups of animals received twelve 4-ms electric field pulses of approximately 37 V/cm (n = 5), 75 V/cm (n = 9) and 150 V/cm (n = 6), respectively. Group 4 was a control group and received a direct application of 2 per cent lidocaine over the sciatic nerve for 30 min. Thermal effects of the shocks were negligible. The sensory refractory spectrum shows that electrical shock damage was mainly to the large, fast myelinated fibres and that higher field strengths do more damage. Also in a histological examination it was found that the more heavily shocked myelinated fibres had sustained more damage.

Control analysis of glycolytic oscillations

The principles involved in the control of the frequency of sustained metabolic oscillations are developed in the context of glycolytic oscillations in Saccharomyces cerevisiae. To this purpose, an existing mathematical model that describes the experimentally obtained oscillations was simplified to a core model. Frequency, relative phase, average concentrations and amplitudes of the oscillations were well approximated by writing the two remaining metabolic variables of the core model (representing [ATP] and [hexose]) as harmonic functions of time and by requiring them to fulfill the differential equations. The extent to which an enzyme (-conglomerate) controls the frequency in a sustained oscillation is defined as the log-log derivative of that frequency with respect to enzyme activity. In both the full model and the core model this control of frequency and the control over the average concentrations proved to be distributed over the enzymes. We identified a summation theorem, stating that the sum of such control coefficients over all processes equals unity for frequency and zero for the average concentrations.

The alpha 2 adrenoreceptor agonist clonidine suppresses seizures, whereas the alpha 2 adrenoreceptor antagonist idazoxan promotes seizures: pontine microinfusion studies of amygdala-kindled kittens

This is the first report showing that microinfusion of alpha 2 adrenoreceptor agonists and antagonists into the vicinity of the locus ceruleus (LC) have contrasting effects on evoked amygdala-kindled seizure susceptibility. Microinfusion (1 microliter) of the alpha 2 agonist clonidine (CLON) and of the alpha 2 antagonist idazoxan (IDA) were made over 1 min through cannulae in the LC ipsilateral to the kindled amygdala in 6 kittens. Order of administered drugs (CLON vs. IDA) and dosages (n = 3 each) were partly counterbalanced. Focal and convulsive seizure thresholds were evaluated 10-12 min post-infusion and compared to thresholds obtained during two, interspersed control conditions (vehicle control = 1 microliter microinfusion of sterile saline; sham control = needle insertion only). CLON significantly elevated focal and generalized seizure thresholds, whereas IDA significantly reduced seizure thresholds when compared to controls. Magnitude of effects was dose-dependent. These findings confirm that norepinephrine (NE) is a potent antiepileptic agent. Results also suggest that pontine microinfusions could eventually provide an alternative treatment option for medically refractory limbic epilepsy.

The alpha 2-adrenoreceptor agonist clonidine suppresses seizures, whereas the alpha 2-adrenoreceptor antagonist idazoxan promotes seizures in amygdala-kindled kittens: a comparison of amygdala and pontine microinfusion effects

PURPOSE

We sought to determine whether local, in vivo microinfusion of an alpha 2-adrenoreceptor agonist and antagonist into either the amygdala or the pons (locus ceruleus, LC) would have contrasting effects on evoked amygdala-kindled seizure susceptibility.

METHODS

The study population consisted of 6 amygdala-kindled kittens, each undergoing the same protocol, in which the amygdala microinfusion paradigm preceded the pontine microinfusion series. Microinfusions (1 microliter) of the alpha 2-agonist clonidine (CLON) and the alpha 2-antagonist idazoxan (IDA) were made over 1 min through cannulas adjacent to stimulating electrodes in the kindled amygdala or through cannulas adjacent to recording electrodes in the ipsilateral LC. Order of administered drugs (CLON vs. IDA) and dosages (n = 3 each) was partly counterbalanced. Focal and convulsive seizure thresholds were evaluated 10-12 min postinfusion and compared to thresholds obtained during two interspersed control conditions (vehicle control = 1 microliter microinfusion of sterile saline; sham control = needle insertion only).

RESULTS

CLON significantly increased focal and generalized seizure thresholds, whereas IDA significantly reduced seizure thresholds when compared to controls. Magnitude of effects was dose dependent and more potent after pontine than amygdala microinfusion.

CONCLUSIONS

Our results confirm and extent findings of previous researchers who used unlocalized in vivo manipulations to show that norepinephrine (NE) is a highly antiepileptic agent in the amygdala kindling preparation. With further investigation, the results may ultimately lead to development of microinfusion techniques as an alternative treatment option for limbic epilepsy.

Relation between rise times and amplitudes of GABAergic postsynaptic currents

1. We recorded rise times and amplitudes of spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) in melanotropes of Xenopus laevis. Average rise times did not vary with amplitude, but the rise times of larger IPSCs were less variable. A simple linear one-step Markov model for channel opening following the binding of a transmitter molecule can quantitatively account for the average rise time and its coefficient of variation as a function of amplitude. Our results indicate that the observed variations in the rise times are not due to variations in transmitter concentrations, but result from stochastic variations in the opening of the receptor channels.

Mechanochemical coupling of the motion of molecular motors to ATP hydrolysis

The typical biochemical paradigm for coupling between hydrolysis of ATP and the performance of chemical or mechanical work involves a well-defined sequence of events (a kinetic mechanism) with a fixed stoichiometry between the number of ATP molecules hydrolyzed and the turnover of the output reaction. Recent experiments show, however, that such a deterministic picture of coupling may not be adequate to explain observed behavior of molecular motor proteins in the presence of applied forces. Here we present a general model in which the binding of ATP and release of ADP serve to modulate the binding energy of a motor protein as it travels along a biopolymer backbone. The mechanism is loosely coupled--the average number of ATPs hydrolyzed to cause a single step from one binding site to the next depends strongly on the magnitude of an applied force and on the effective viscous drag force. The statistical mechanical perspective described here offers insight into how local anisotrophy along the "track" for a molecular motor, combined with an energy-releasing chemical reaction to provide a source of nonequilibrium fluctuations, can lead to macroscopic motion.

Paroxysmal microarousals in amygdala-kindled kittens: could they be subclinical seizures?

Amygdala-kindled kittens exhibit frequent epileptiform EEG transients, often in conjunction with phasic arousal events of sleep [k-complexes, pontogeniculo-occipital (PGO) waves, and/or sleep spindles]. In this study, paroxysmal microarousals occurred throughout the sleep-wake cycle after kindling, but were most frequent during seizure-prone states of slow-wave sleep (SWS) and the transition into rapid-eye-movement sleep (REM). Their incidence correlated with interictal sleep fragmentation as well as onset of spontaneous convulsions. Results could reflect transsynaptic kindling effects on brainstem and forebrain arousal mechanisms with which amygdala is reciprocally connected. Increased discharge rates of neural generators for normal EEG and behavioral arousal could disrupt sleep at some times and recruit epileptic neurons in the kindled focus to precipitate seizures at others. Alternatively, epileptiform EEG paroxysms were accompanied by subtle behavioral stereotypes (a head nod, limb elevation, eye twitch, lip smack, or a combination of these). Behavioral correlates were elements of partial kindled seizures, suggesting that paroxysmal microarousals may be subclinical seizures. Whether or not the microarousals are true seizures, our findings may link ictal onset and interictal sleep disorders to a subclinical paroxysmal arousal disorder and suggest a common epileptic mechanism.

Variance analysis of gamma-aminobutyric acid (GABA)-ergic inhibitory postsynaptic currents from melanotropes of Xenopus laevis

We have studied the variance in the decay of large spontaneous gamma-aminobutyric acid (GABA)-ergic inhibitory postsynaptic currents (IPSCs) in melanotropes of Xenopus laevis to obtain information about the number of GABAA receptor channels that bind GABA during the IPSCs. The average decay of the IPSCs is well described by the sum of two exponential functions. This suggests that a three-state Markov model is sufficient to describe the decay phase, with one of the three states being an absorbing state, entered when GABA dissociates from the GABAA receptor. We have compared the variance in the decay of large spontaneous IPSCs with the variance calculated for two different three-state models: a model with one open state, one closed state, and one absorbing state (I), and a model with two open states and one absorbing state (II). The data were better described by the more efficient model II. This suggests that the efficacy of GABA at synaptic GABAA receptor channels is high and that only a small number of channels are involved in generating the GABA-ergic IPSCs.

The alpha 2-agonist clonidine suppresses seizures, whereas the alpha 2-antagonist idazoxan promotes seizures--a microinfusion study in amygdala-kindled kittens

This is the first report showing that local, in vivo microinfusion of alpha 2-adrenoreceptor agonists and antagonists have contrasting effects on amygdala-kindled seizure susceptibility. Microinfusions (1 microliter) of the alpha 2-agonist clonidine (CLON) and of the alpha 2-antagonist idazoxan (IDA) were made over 1 min through cannulae adjacent to stimulating electrodes in five amygdala-kindled kittens. Order of administered drugs (CLON vs. IDA) and dosages (n = 3 each) was partly counterbalanced. Focal and convulsive seizure thresholds were evaluated 10-12 min post-infusion and compared to thresholds obtained during two, interspersed control conditions (vehicle control: 1 microliter microinfusion of sterile saline; sham control: needle insertion only). CLON significantly elevated focal and generalized seizure thresholds, whereas IDA significantly reduced seizure thresholds when compared to controls. Magnitude of effects was dose-dependent. Results confirm and extend previous findings which employed unlocalized, in vivo manipulations to show that norepinephrine is a potent antiepileptic agent in the amygdala kindling preparation.

A new buffering system and its use in electrophoresis and isoelectric focusing

A novel buffer system with rather unique properties particularly well suited for preparative isoelectric focusing is described. The system was developed in response to the long standing need for pH gradients formulated using inexpensive components of known chemical composition. The system is binary consisting of buffer pairs covering the pH range of 3 to 10, in increments of less than 1 pH. The components are all readily available, nontoxic, and biologically acceptable, and are selected on the basis of their dissociation constants. The requirement for each buffer pair is that there be an overlapping pH zone where both components are largely non-ionized, having a ratio of neutral species to total buffer concentration between about 0.90 and 0.99. This ratio is defined as the 'electrophoretic reserve capacity' (ERC). Within the above ERC range a stable pH gradient is obtained, assuring sharply resolved protein focusing. Buffer parameters, mainly pH, buffering capacity, ERC, transport numbers, and conductivity, can be easily calculated and the buffer composition adjusted to meet requirements. All components are used at high concentration, typically of the order of up to 100 mM, yielding buffering capacities and conductivities analog to those customary in electrophoresis.

Counterflow in isotachophoresis: computer simulation and experimental studies

A computer model has been developed to predict the effects of co- and counter-current flows on electrophoretic transport. Model predictions are compared with experimental data obtained with the large-scale recycling isotachophoresis apparatus, recently developed in our laboratory. There were no significant changes in the steady state properties or the transient development of the Kohlrausch-adjusted profiles with and without flow. The application of counterflow in free flow isotachophoresis in early stages, before a steady state is achieved, can result in selective wash-out of slower sample components. Thus, the magnitude of counterflow can be used as a variable in optimizing separations. The characteristic features of the model render it also suitable for the simulation of electroosmotic flow in capillary electrophoresis in open tubes, where plug-type flow prevails.

Recycling isoelectric focusing: use of simple buffers

Using the recycling free-flow focusing (RF3) apparatus, we have demonstrated that single ampholytes can be utilized to establish very stable pH regions, separating all proteins into three groups: a sharply resolved zone of proteins isoelectric at the prevailing pH, this "pH window" being bracketed by zones of more acidic and/or basic proteins. The ampholytes used are either amino acids or their dipeptides and other derivatives. Where necessary, because of lack of an ampholyte with the required pH, a binary mixture of ampholytes can be utilized. The closer their isoelectric points (pI), the narrower will be the pH window, i.e., the sharper the resolution of the bracketed proteins. This method overcomes the necessity of using ill-defined commercial carrier ampholytes, such as Ampholine, for preparative isoelectric focusing. It is recommended that the ampholytes be utilized at relatively high concentration, 100mM or higher, this contributing to pH stability and minimizing protein precipitation.

Membrane active plasma factor in multiple sclerosis: characterization and isolation by recycling isoelectric focusing

Recycling isoelectric focusing is a rapid, high resolution technique that has the capability of fractionating complex mixtures of proteins on a preparative scale on the basis of their isoelectric points (pIs). For this reason, it appeared to be an ideal tool to further characterize and isolate the surface active plasma component(s) which is abnormal in multiple sclerosis (MS). The normal control and the abnormal MS plasma components, or factors, proved to be stable under the conditions used in this technique, including deionization by electrodialysis, dialysis against distilled water, lyophilization and the presence of 3M urea and carrier distilled water, lyophilization and the presence of 3M urea and carrier ampholytes. The presence or absence of plasma factor activity was determined by incubating red blood cells in a test plasma, or plasma fraction, followed by the determination of the red blood cell electrophoretic mobility in the presence and absence of linoleic acid. Both the normal and MS factor had a pI of 4.0 +/- 0.1 under the conditions used. A high degree of purification was achieved and albumin was eliminated as a possible candidate for the factor(s).

Electrophoretic transport of solutes in aqueous two-phase systems

Electrophoretic transport of proteins across the interface between the phases of an aqueous polymer two-phase system can be greatly impeded in comparison with transport within the individual phase. This effect can be controlled by modifying the affinity of the protein for a phase by suitable manipulations of such variables as pH. The effect is not caused by differences in the electrophoretic velocity between the two phases, nor by large changes in pH at the interface. An analogy exists between this phenomenon and the related subject of diffusion of electrolytes across the phase interface.

Computer simulation and experimental validation of the electrophoretic behavior of proteins

A mathematical model of the electrophoretic behavior of proteins is presented. The Debye-Hückel-Henry theory is used for the description of protein mobility, which has the important result of making net mobility a function of ionic strength. A net charge vs pH relationship and a diffusion coefficient are required to describe a specific protein. The model is employed for the computer simulation of three distinct electrophoretic modes: isoelectric focusing, isotachophoresis, and zone electrophoresis. The validity of the model is tested by comparing simulation with experimental data. Excellent qualitative agreement was found.

Purification of lentil lectins using preparative electrophoresis

Electrophoresis presents an interesting alternative to chromatography for the purification of biological compounds. To document the performance of three preparative electrophoresis apparatus currently available, they were applied to the purification of lectins from lentil seeds which contain two isolectins usually purified by chromatography. Purification by electrophoresis consists of first isolating a mixture of the two isolectins and then separating them. For the first step, either of two free-flow electrophoresis apparatus were employed: the Elphor VaP 22, using field step electrophoresis and the Biostream using zone electrophoresis. To optimize the process, the Biostream was modified to a recycling mode. This required repositioning one dialysis membrane which separates an electrode from the separation chamber. This allowed the lentil extract to be desalted by electrodialysis directly in the apparatus prior to fractionation. A high concentration of lectins was collected at the cathode and acidic proteins were collected at the anode. The bulk of the extract was recycled until the whole volume was processed. In a second step the isolectins were separated by recycling isoelectric focusing in the recycling isoelectric focusing apparatus. The present work clearly demonstrates that electrophoretic methods provide lectins with higher purity than chromatographically purified commercial products.

Isolation of monoclonal antibodies to phencyclidine from ascites fluid by preparative isoelectric focusing in the Rotofor

A monoclonal antibody to phencyclidine was developed, produced in mouse ascites fluid, and purified. The purification used only preparative-scale isoelectric focusing in the Rotofor and dialysis. In 4 h, 25% (4 mg) of the antibody from 10 ml of ascites fluid was purified to homogeneity while 63% of the total antibody was recovered.

Low-level fetal lead exposure effect on neurobehavioral development in early infancy

A prospective method was used in this study to assess the effects of fetal lead exposure on neurodevelopmental status in 3- and 6-month old infants. At their first prenatal medical appointments, 305 lower socioeconomic status women residing in predesignated lead-hazardous areas of Cincinnati were recruited. Lead was measured in whole blood in both the mother and fetal-placental unit (prenatal and cord) and the neonate (ten days and 3 months). All blood lead levels were less than 30 micrograms/dL. Infant development was assessed with the Bayley scales at 3 and 6 months of age. Multiple regression analyses which treated perinatal health factors such as birth weight and gestation as confounders indicated an independent, inverse relationship between both prenatal and neonatal blood lead levels and performance on the Bayley Mental Developmental Index at both ages. Male infants and infants from the poorest families appeared to be especially sensitive to these psychoteratogenic influences. Further study using a structural equations approach indicated that neurobehavioral deficits were partly mediated by lead-related reductions in birth weight and gestation.

Automatic thoughts questionnaire: a study of concurrent validity

To investigate the concurrent validity of the Automatic Thoughts Questionnaire, 82 college students completed this measure, the Repression-Sensitization Scale, Novaco's Anger Inventory, a Pleasant Activities Scale, and the Family Environment Scale. Scores on the Automatic Thoughts Questionnaire correlated with those on the Repression-Sensitization Scale and with several subscales of the Family Environment Scale, but not with scores on the Anger or Pleasant Activities Scales. Results were interpreted as providing minimal support for the test's validity.

Characterization of synthetic carrier ampholytes by repetitive scanning of the electric field during focusing

This paper reports the utilization of a potential gradient array detector for monitoring the dynamics of the electric field during isoelectric focusing. Transient and steady state electric field profiles are presented for synthetic carrier ampholyte mixtures with a wide (approximately 3-10) pH range. Two available commercial products (Ampholine and Pharmalyte) and a laboratory synthesized mixture (PEHA ampholytes) are compared. The formation of conductivity gaps and their migration toward the cathode in extended experiments (cathodic drift) can be visualized with this system.

Electrophoresis: mathematical modeling and computer simulation

A mathematical model of electrophoretic separation processes has been developed and adapted for computer simulations. The model is used to predict the characteristic behavior of a variety of electrophoretic techniques from a knowledge of chemical equilibria and physical transport phenomena. The model provides a unifying basis for a rational classification of all electrophoretic processes.

Properties of narrow-range ampholytes isolated from wide-range ampholyte preparations

A simple procedure for obtaining useful narrow-pH-range ampholytes from inexpensive laboratory-synthesized ampholytes by preparative isoelectric focusing in Pevikon is described. The narrow-range ampholytes prepared in this way are comparable to commercial ampholyte preparations as judged by conductivity, buffer capacity, pH gradient formation, and resolving power. These inexpensive narrow-range ampholytes are particularly well suited to preparative isoelectric focusing applications requiring large quantities of ampholytes.

Mathematical model for transient isoelectric focusing of simple ampholytes

A mathematical model describing transient processes in isoelectric focusing (IEF) of L biprotic ampholytes is presented. The model is a generalization of our previous research on steady slate in IEF and consists of L nonlinear partial differential equations coupled with 2L+2 algebraic equations. Constraints imposed by the mode of operation, viz., constant current. voltage or power, are described. Due to the nonlinearity of the equations, analysis of the model requires computer simulation. Model equations suitable for computer implementation are derived.

Mathematical modeling and computer simulation of isoelectric focusing with electrochemically defined ampholytes

A mathematical model of isoelectric focusing at the steady state has been developed for an M-component system of electrochemically defined ampholytes. The model is formulated from fundamental principles describing the components' chemical equilibria, mass transfer resulting from diffusion and electromigration, and electroneutrality. The model consists of ordinary differential equations coupled with a system of algebraic equations. The model is implemented on a digital computer using FORTRAN-based simulation software. Computer simulation data are presented for several two-component systems showing the effects of varying the isoelectric points and dissociation constants of the constituents.

Serum protein fractionation by isotachophoresis using amino acid spacers

Analytical and preparative isotachophoresis has been carried out using amino acids and peptides as discrete spacers in contrast to the usually employed continuous mobility spectrum Ampholine. Analytical isotachoresis in free solution, using the LKB Tachophor, demonstrated the separation of human serum into distinct mobility subgroups, n spacers giving rise to n + 1 protein subgroups. Preparative fractionation on polyacrylamide gel was carried out on the LKB Uniphor using threonine and glycine as spacers. Immunoelectrophoretic analysis showed that eight out of ten proteins assayed were clearly resolved in the three subgroups obtained, thus demonstrating the sharpness of isotachophoretic resolution.

Hypochlorite-induced alterations to canine serum complement

Changes in the concentration of the components of complement produced by NaOC1 both in vitro and in vivo are recorded. C1, C4 and C7 are particularly sensitive to this oxidizing agent, although all components decrease at high concentrations of NaOC1. Following oxidation, complement componenets return rapidly to normal. Data are presented to indicate that part of this repair mechanism is due to the action of reducing agents such as ascorbic acid and part is due to the synthesis of the individual components. The unique sensitivity of complement components to oxidation make this treatment of potential value in suppressing the inflammatory response.