scholarly journals Influence of systematic error on the shape of the Scatchard plot of tRNAPhe binding to eukaryotic ribosomes

1997 ◽  
Vol 325 (2) ◽  
pp. 401-404 ◽  
Author(s):  
Sergei A. NEKHAI ◽  
Vladimir E. BELETZKIJ ◽  
Dmitri M. GRAIFER
Keyword(s):  
Systematic Error ◽  
Model Experiment ◽  
Concentration Ratio ◽  
Scatchard Plot ◽  
Experimental Conditions ◽  
Binding Model ◽  
Small Systematic Error ◽  
Concentration Changes ◽  
Scatchard Plots

Scatchard plots of tRNAPhe binding to poly(U)-programmed human 80 S ribosomes can be curved, either concave upwards or concave downwards, depending on the experimental conditions. The influence of a systematic error on the shape of the Scatchard plots has been analysed in a model experiment where the binding proceeds at two independent sites. The Scatchard plot for this binding model has a concave-upwards shape. When the concentration of the ribosomes is kept constant, a small systematic error in tRNA concentration changes this Scatchard plot markedly to a concave-downwards plot as though a co-operative interaction occurred. In contrast, when the tRNA concentration exceeds the ribosomal concentration and their concentration ratio is constant, the Scatchard plot is stable with respect to the systematic error. We suggest the latter type of experiment to be more appropriate. The results also imply a non-co-operative interaction of tRNAPhe with the 80 S ribosome.

scholarly journals Interaction of phenylthiolato-(2,2′,2′′-terpyridine)platinum(II) cation with DNA

1984 ◽  
Vol 222 (1) ◽  
pp. 203-215 ◽  
Author(s):  
L P G Wakelin ◽  
W D McFadyen ◽  
A Walpole ◽  
I A G Roos
Keyword(s):  
Base Pair ◽  
Equilibrium Dialysis ◽  
Platinum Complexes ◽  
Nucleotide Composition ◽  
Contour Length ◽  
Ligand Molecule ◽  
Experimental Conditions ◽  
Kinetic Measurements ◽  
Binding Isotherms ◽  
Scatchard Plots

The interaction between a novel aromatic thiolato derivative from the family of DNA-intercalating platinum complexes, phenylthiolato-(2,2′,2″-terpyridine)platinum(II)-[PhS(ter py)Pt+], and nucleic acids was studied by using viscosity, equilibrium-dialysis and kinetic measurements. Viscosity measurements with sonicated DNA provide direct evidence for intercalation, and show that at binding ratios below 0.2 molecules per base-pair PhS(terpy)Pt+ causes an increase in contour length of 0.2 nm per bound molecule. However, helix extension diminishes at greater extents of binding, indicating the existence of additional, non-intercalated, externally bound forms of the ligand. The ability of PhS(terpy)Pt+ to aggregate in neutral aqueous buffers at a range of ionic strengths and temperatures was assessed by using optical-absorption methods. Scatchard plots for binding to calf thymus DNA at ionic strength 0.01 (corrected for dimerization) are curvilinear, concave upward, providing further evidence for two modes of binding. The association constant decreases at higher ionic strengths, in accord with the expectations of polyelectrolyte theory, although the number of cations released per bound unipositive ligand molecule is substantially greater than 1. Stopped-flow kinetic measurements confirm the complexity of the binding reaction by revealing multiple bound forms of the ligand whose kinetic processes are both fast and closely coupled. Thermal denaturation of DNA radically alters the shapes of binding isotherms and either has little effect on, or enhances, the affinity of potential binding sites, depending on experimental conditions. Scatchard plots for binding to natural DNA species with differing nucleotide composition show that the ligand has a requirement for a single G X C base-pair at the highest-affinity intercalation sites.

Regulation of inositol 1,4,5-trisphosphate-induced Ca2+ release. I. Effect of Mg2+

1990 ◽  
Vol 258 (6) ◽  
pp. C1077-C1085 ◽  
Author(s):  
P. Volpe ◽  
B. H. Alderson-Lang ◽  
G. A. Nickols
Keyword(s):  
Dependent Manner ◽  
Differential Centrifugation ◽  
Michaelis Constant ◽  
Experimental Conditions ◽  
Concentration Dependent Manner ◽  
Apparent Affinity ◽  
Inositol 1,4,5 Trisphosphate ◽  
Noncompetitive Inhibitor ◽  
Scatchard Plots ◽  
Microsomal Pellet

Canine cerebellar membranes were fractionated by differential centrifugation into a crude mitochondrial pellet (P2) and a crude microsomal pellet (P3). The effect of Mg2+ on inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release and [3H]IP3 binding was assessed. Mg2+ inhibited IP3-induced Ca2+ release in a concentration-dependent manner. Mg2+ influenced both the extent of IP3-induced Ca2+ release and the apparent affinity for IP3. A 10-fold change of free Mg2+ (from approximately 30 to approximately 300 microM) reduced the extent of Ca2+ release by two- to threefold and shifted the apparent Michaelis constant from approximately 0.5 to approximately 0.9 microM IP3. Thus Mg2+ seemed to be noncompetitive inhibitor of IP3-induced Ca2+ release. Mg2+ also inhibited Ca2+ release elicited by glycerophosphoinositol 4,5-bisphosphate, a poorly metabolized analogue of IP3. Mg2+ and heparin sodium were shown to be additive inhibitors of IP3-induced Ca2+ release. Mg2+ inhibited [3H]IP3 binding under experimental conditions designed to minimize IP3 hydrolysis. Scatchard plots indicated that 0.5 mM free Mg2+ reduced maximum binding from 10.9 to 3.5 pmol IP3 bound/mg protein and increased the dissociation constant from 136 to 227 nM. The modulation of [3H]IP3 binding and IP3-induced Ca2+ release by Mg2+ could be physiologically relevant.

scholarly journals A role for adenosine in metabolic depression in the marine invertebrate Sipunculus nudus

1997 ◽  
Vol 272 (1) ◽  
pp. R350-R356 ◽  
Author(s):  
A. Reipschlager ◽  
G. E. Nilsson ◽  
H. O. Portner
Keyword(s):  
Body Wall ◽  
Marine Invertebrate ◽  
Coelomic Fluid ◽  
Metabolic Depression ◽  
O2 Consumption ◽  
Experimental Conditions ◽  
Indwelling Catheter ◽  
Sipunculus Nudus ◽  
Body Wall Musculature ◽  
Concentration Changes

Involvement of neurotransmitters in metabolic depression under hypoxia and hypercapnia was examined in Sipunculus nudus. Concentration changes of several putative neurotransmitters in nervous tissue during anoxic or hypercapnic exposure or during combined anoxia and hypercapnia were determined. Among amino acids (gamma-aminobutyric acid, glutamate, glycine, taurine, serine, and aspartate) and monoamines (serotonin, dopamine, and norepinephrine), some changes were significant, but none were consistent with metabolic depression under all experimental conditions applied. Only the neuromodulator adenosine displayed concentration changes in accordance with metabolic depression under all experimental conditions. Levels increased during anoxia, during hypercapnia, and to an even greater extent during anoxic hypercapnia. Adenosine infusions into coelomic fluid via an indwelling catheter induced a significant depression of the normocapnic rate of O2 consumption from 0.36 +/- 0.04 to a minimum of 0.24 +/- 0.02 (SE) mumol.g-1.h-1 after 90 min (n = 6). Application of the adenosine antagonist theophylline caused a transient rise in O2 consumption 30 min after infusion during hypercapnia but not during normocapnia. Effects of adenosine and theophylline were observed in intact individuals but not in isolated body wall musculature. The results provide evidence for a role of adenosine in inducing metabolic depression in S. nudus, probably through the established effects of decreasing neuronal excitability and neurotransmitter release. In consideration of our previous finding that metabolic depression in isolated body wall musculature was elicited by extracellular acidosis, it is concluded that central and cellular mechanisms combine to contribute to the overall reduction in metabolic rate in S. nudus.

A wire spark chamber capacitive readout system with low leakage current and small systematic error

1983 ◽  
Vol 206 (1-2) ◽  
pp. 135-145
Author(s):  
H.B. Anderhub ◽  
J. Boecklin ◽  
H.P. von Gunten ◽  
H. Koenig ◽  
P. Le Coultre ◽  
...  
Keyword(s):  
Systematic Error ◽  
Leakage Current ◽  
Readout System ◽  
Low Leakage ◽  
Low Leakage Current ◽  
Small Systematic Error

Recirculatory Spinal Subarachnoid Perfusions in Dogs

Neurosurgery ◽  
1977 ◽  
Vol 1 (1) ◽  
pp. 48-56 ◽  
Author(s):  
Frederick H. Sklar ◽  
Donlin M. Long
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Albumin Concentration ◽  
Syringe Pump ◽  
Experimental Conditions ◽  
Ventriculocisternal Perfusion ◽  
Resting Pressure ◽  
In Series ◽  
Intracranial Pressures ◽  
Concentration Changes

Abstract Open-ended ventriculocisternal perfusion techniques for determining cerebrospinal fluid production and absorption rates are severely restricted by the absolute requirement that steady state conditions be present. A new closed recirculatory spinal perfusion technique is described. Because steady state equilibrium is not necessary, numerous determinations at multiple intracranial pressures or under varied experimental conditions are possible within relatively brief perfusion periods. Cerebrospinal fluid (CSF) and nondiffusible albumin tracer are rapidly recirculated through the spinal subarachnoid space in a cephalad direction. The concentration of fluorescein-tagged albumin is continuously monitored as the CSF is circulated through a fluorometric flow cell. Measured continuously, intracranial pressure (ICP) is regulated by changing the volume of the external perfusion circuit with a syringe pump connected in series to the recirculatory spinal perfusion. CSF formation and absorption rates are calculated from measurements of albumin concentration, concentration changes with time, ICP, syringe pump infusion rate, and the external perfusion circuit volume. In dogs, data can be collected after only 45 minutes for mixing; perfusions at four or five intracranial pressures in addition to normal resting pressure can be completed within 2 to 3 hours. The data from 15 perfusions in 14 dogs are presented. The method provides normal resting pressure values of CSF production and absorption consistent with those values in the literature determined by traditional ventriculocisternal perfusion techniques. Determinations at multiple intracranial pressures suggest a proportional relationship between absorption and ICP. No consistent acute change in CSF formation with pressures to 50 mm Hg can be inferred from these data.

scholarly journals Technical note: CO<sub>2</sub> is not like CH<sub>4</sub> – limits of and corrections to the headspace method to analyse <i>p</i>CO<sub>2</sub> in water

2020 ◽  
Author(s):  
Matthias Koschorreck ◽  
Yves T. Prairie ◽  
Jihyeon Kim ◽  
Rafael Marcé
Keyword(s):  
Systematic Error ◽  
Headspace Analysis ◽  
Technical Note ◽  
Simple Application ◽  
Carbonate System ◽  
Experimental Conditions ◽  
Potential Error ◽  
Chemical Theory ◽  
Different Types ◽  
Chemical Equilibration

Abstract. Headspace analysis of CO2 frequently has been used to quantify the concentration of CO2 in freshwater. According to basic chemical theory, not considering chemical equilibration of the carbonate system in the sample vials will result in a systematic error. In this paper we provide a method to quantify the potential error resulting from simple application of Henry's law to headspace CO2 samples. By analysing the potential error for different types of water and experimental conditions we conclude that the error incurred by headspace analysis of CO2 is less than 5 % for samples with pH 

A method for simultaneous catheterization of major hepatic vessels in a chronic canine preparation

1959 ◽  
Vol 196 (2) ◽  
pp. 311-314 ◽  
Author(s):  
William C. Shoemaker ◽  
William F. Walker ◽  
Theodore B. Van Itallie ◽  
Francis D. Moore
Keyword(s):  
Operative Technique ◽  
Blood Sampling ◽  
Experimental Conditions ◽  
Feasible Method ◽  
Hepatic Vessels ◽  
Concentration Changes ◽  
Liver Biopsies

A feasible method for measuring concentration changes of various substances as they enter and leave the liver is described together with the operative technique. This preparation allows simultaneous sampling of blood from all major hepatic vessels in the in vivo, unanesthetized dog under chronic experimental conditions. A modification of this technique is described whereby liver biopsies may be obtained at the same time as the blood sampling.

Algorithm Establishment with Model Experiment for Continuous-Wave Functional Near-Infrared Spectroscopy

2011 ◽  
Vol 138-139 ◽  
pp. 553-559
Author(s):  
Ting Li ◽  
Zhi Li Zhang ◽  
Yi Zheng
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Model Experiment ◽  
Near Infrared ◽  
Continuous Wave ◽  
Valsalva Maneuver ◽  
Hemoglobin Concentration ◽  
Functional Near Infrared Spectroscopy ◽  
Concentration Changes

Although functional near-infrared spectroscopy (fNIRS) has been developing as a useful tool for monitoring functional brain activity since the early 1990s, the quantification of hemoglobin concentration changes is still controversial and there are few detailed reports especially for continuous-wave (CW) instruments. By means of a two-layer model experiment mimicking hemodynamic changes in brain and mathematical analysis based on the modified Beer-Lambert law, we established an algorithm for a CW functional near-infrared spectroscopy (CW-fNIRS). The accuracy of this algorithm was validated both in comparison with direct measurements on brain tissue model and in vivo measurement upon human valsalva maneuver. This described method can also be utilized for other CW-fNIRS instruments to establish measuring algorithm.

scholarly journals Amino acid uptake in the developing chick embryo heart. The effect of insulin on glycine and leucine accumulation

1968 ◽  
Vol 107 (4) ◽  
pp. 575-580 ◽  
Author(s):  
G. G. Guidotti ◽  
G. Gaja ◽  
L. Loreti ◽  
G. Ragnotti ◽  
D. A. Rottenberg ◽  
...  
Keyword(s):  
Amino Acid ◽  
Chick Embryo ◽  
Concentration Ratio ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Experimental Conditions ◽  
Insulin Effect ◽  
Chick Embryo Heart ◽  
Embryo Heart

1. The accumulation of [1−14C]glycine and the uptake, accumulation, incorporation (into protein, lipid, glycogen) and oxidation of l-[1−14C]leucine in 5-day-old chick embryo hearts were investigated in vitro, and the effects of insulin, puromycin and 4-methyl-2-oxopentanoic acid on these processes were studied. 2. With glycine, the ratio of concentration of the labelled amino acid in the cell water to that in medium markedly exceeded unity. Insulin significantly increased this ratio. Puromycin did not prevent the insulin effect. 3. With leucine, the concentration ratio of the labelled amino acid between intracellular and extracellular water approached unity in the absence of puromycin and was doubled by its presence. In neither case did insulin substantially alter this ratio. The addition of 4-methyl-2-oxopentanoic acid had no effect in the absence of insulin, but produced a significant increase of the concentration ratio in the presence of the hormone. 4. Leucine uptake was increased slightly by insulin in all experimental conditions except in the presence of puromycin, where a more pronounced stimulation was observed. The hormone had no effect on the incorporation of the labelled amino acid into protein, but accelerated its oxidation to carbon dioxide; the latter effect was particularly evident in the presence of puromycin and disappeared after the addition of 4-methyl-2-oxopentanoic acid.

scholarly journals Controllable Synthesis of Silver Nanoparticles Using Three-Phase Flow Pulsating Mixing Microfluidic Chip

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Guojun Liu ◽  
Xiang Ma ◽  
Xiaodong Sun ◽  
Yanhui Jia ◽  
Tengfei Wang
Keyword(s):  
Silver Nitrate ◽  
Microfluidic Chip ◽  
Concentration Ratio ◽  
Synthesis Method ◽  
Synthesis Temperature ◽  
Controllable Synthesis ◽  
Experimental Conditions ◽  
Three Phase ◽  
Inlet Flow Rate ◽  
Three Phase Flow

On the basis of liquid-phase reduction mechanism, a novel synthesis method to prepare silver nanoparticles (AgNPs) is proposed, which uses piezoelectric-actuated three-phase flow pulsating mixing microfluidic chip. In order to study and explore the influence of different factors on the synthesis of AgNPs, a series of related synthesis experiments were carried out. The corresponding experimental conditions include the concentration of sodium hydroxide and reducing agent solution, polyvinylpyrrolidone (PVP) dosage, inlet flow rate, and synthesis temperature. The synthesized AgNPs were characterized by the UV-Vis absorption spectrophotometer and transmission electron microscopy. The effects of different experimental conditions on the controllable synthesis of AgNPs were analyzed, and the optimum synthesis conditions of AgNPs were obtained. Experimental results show that the spherical AgNPs with an average particle diameter of about 29 nm, high yield, fine morphology, and good monodispersity were synthesized using the microfluidic chip under the conditions of the working frequency (200 Hz), the initial concentration of silver nitrate (1 mM), the synthesis temperature (80°C), the concentration ratio of sodium hydroxide to silver nitrate (2 : 1), the concentration ratio of glucose to silver nitrate (4 : 1), the inlet flow rate (3.5 ml/min), and the quality ratio of PVP to silver (more than 1 : 1). The related research shows that it is an efficient synthesis method to develop the controllable synthesis experiments of AgNPs under multifactors using the three-phase pulsating mixing microfluidic chip.

Sign in / Sign up

Export Citation Format

Share Document