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PubMed2002

Toxicological study of a glucose-added acetic acid maintenance infusion solution (VEEN 3G Inj.) local irritation test.

The local irritating effect of Veen 3G Inj. (glucose-added acetic acid maintenance infusion solution) was examined in male rabbits. We studied the local irritating effect of the infusion solution compared with that of Ringer's solution, 5% sulfobromophthalein sodium injection, distilled water for injection or glucose-added Ringer's solution. In the vascular irritation test, macroscopical and histopathological changes induced by the infusion solution were not observed in the vessels. Moreover, in the hemolytic test, hemolysis of rabbit erythrocyte was not observed in the mixture with the infusion solution. In the present study, no change suggesting irritation by the infusion solution was observed in the in vivo vascular irritation test using the auricular vein of rabbits or in the in vitro hemolytic test using rabbit erythrocyte. In conclusion, in clinical use the infusion solution produces extremely slight adverse effects, such as vessel pain and phlebitis on the injection site.

Animals↗
PubMed2003

[The protective role of hyperoxic Ringer's solution on the hepatic injury in rats with burn shock].

OBJECTIVE: To explore the dynamic postburn changes in rat hepatic function and the effects of hyperoxic Ringer's solution resuscitation on the function. METHODS: One hundred and ninety Wistar rats of both sexes with body weight of 250 - 300 g were employed as the model and were divided into 6 groups as A, B, C, D, E and F groups as follows: normal control (A, n = 10), early resuscitation with Ringer's solution (B, n = 40), delayed resuscitation with Ringer's solution (C, n = 30), early resuscitation with hyperoxic Ringer's solution (D, n = 40), delayed hyperoxic Ringer's solution resuscitation (E, n = 30) and burn control (F, n = 40). Blood samples were drawn from the injured rats under anesthesia at 6, 12, 24 and 48 postburn hours (PBHs), and the serum contents of ALT, AST and MDA in these blood samples were determined. Hepatic tissue samples were also harvested at the same time and served histologically. RESULTS: The plasma ALT level at 6 PBH in all groups was higher than that in A group (P < 0.05). There was significant difference of plasma ALT levels between hyperoxic Ringer's solution treatment group an other treatment groups (P < 0.05). And there was evident difference of plasma ALT levels between hyperoxic Ringer's solution treatment groups and other treatment groups (P < 0.05). The dynamic change in plasma AST was almost similar to that of ALT. The plasma MDA level was increased obviously after injury, especially in F group (highest level). Furthermore, the MDA level in C group was higher than that in B group. The plasma MDA levels in D and E groups were evidently lower than that in all other groups (P < 0.05). It was revealed by histological examination that there were different degrees of degeneration an necrosis of hepatocytes during early postburn stage, but less so in D group. CONCLUSION: Fluid resuscitation during early postburn stage with hyperoxic Ringer's solution could inhibit the production of oxygen free radicals and blunt lipid peroxidation, and it could also enhance the host tolerance to hypoxia and prevent hepatocytes from injury, thus hepatic function was protected.

Animals↗
PubMed1992

Effects of oxygenated cardioplegic solutions on myocardial aerobic metabolism.

Oxygenated cardioplegic solutions can deliver sufficient oxygen to support aerobic metabolism of heart tissue during cardiac arrest, but little is known about oxygen use after cardioplegic solution infusion. Exhaustion of myocardial oxygen stores after infusion of oxygenated crystalloid cardioplegic solution or Krebs-Henseleit buffer was measured in rat hearts. Since nicotinamide adenine dinucleotide accumulates when mitochondria become anaerobic, the epicardium was monitored during perfusion and ischemia. As ischemia progressed, nicotinamide adenine dinucleotide fluorescence increased, indicating exhaustion of oxygen. After buffer perfusion, at 37 degrees C, 50% of peak fluorescence was seen at 13 +/- 1 seconds and 90% at 37 +/- 3 seconds. Oxygenated cardioplegic solution increased these intervals to 57 +/- 6 and 114 +/- 9 seconds, respectively. Oxygenated cardioplegic solution at 10 degrees C increased the time to 50% fluorescence to 238 +/- 12 seconds and to 90% to 320 +/- 14 seconds. Differences between buffer and cardioplegic solution were less at 10 degrees C. Aerobic metabolism was completely abolished 6 minutes after infusion of 10 degrees C oxygenated cardioplegic solution. Maintenance of continuous aerobic metabolism during surgical cardiac arrest would require frequent administration of oxygenated crystalloid cardioplegic solution.

Aerobiosis↗
PubMedDate not supplied

[Gastric emptying and metabolic acidosis. I. Study of an experimental model in rats, using an ammonium chloride solution administered through the orogastric route].

The goal of the study was get an experimental model of metabolic acidosis which was appropriated in future gastric emptying studies. For this proposal were utilized 141 female Wistar rats in three stages: in the first (n = 27) was defined the installation, manutention and spontaneous recuperation of the metabolic acidosis produced by the orogastric infusion of a two ml by 100 g of an 0.5 M ammonium chloride solution; in the second (n = 60), it was studied the gastric emptying of the same solution utilized in the first stage and in the last stage (n = 54) it was determined the gastric emptying of the water, for excluding the possibility that the acidificant solution had caused any lesion in the gastric mucosa. As control group were utilized animals fed as a sodium chloride solution in the same concentration and volume that the acidificant solution. The results showed that 6 hours after the infusion, the gastric emptying of two above mentioned meals was complete and there was still a moderate metabolic acidosis in the group with infusion of ammonium chloride solution. Further more, the metabolic acidosis persisted in moderate values until 8 hours after the infusion. Based on these data the interval between 6 and 8 hours after the infusion of the these solutions was considered the best to the further studies about metabolic acidosis and gastric emptying. Finally, the gastric emptying of water, studied in rats with acidosis and controls demonstrated no differences between them. This was interpreted as a clue that the ammonium chloride solution did not modificate the integrity of the gastric mucosa.

Acidosis↗
PubMed1988

Duodenal resistance to the emptying of various solutions from the isolated cat stomach.

Experiments were conducted to determine to what extent the duodenum resists the emptying of various solutions from the isolated stomach. Cat stomachs were maintained in Krebs solution in vitro, and filled with 100 ml isotonic saline solution, isotonic glucose, hypertonic saline solution, hypertonic glucose, or dilute acid. Gastric pressure was constantly monitored; gastric output was collected constantly by a cannula in the proximal or distal duodenum. For all solutions, cumulative gastric output at all times was considerably less with the distal than the proximal cannula position. This difference was almost entirely caused by a smaller fractional gastric output during the first minute of gastric emptying, and by reduced amplitude of the gastric stroke volume with the distal cannula position. Some differences were observed in the gastric emptying rate for the various solutions; isotonic saline solution emptied particularly slowly and hydrochloric acid emptied particularly fast. In addition, the various solutions produced different gastric pressure patterns, which could not be entirely explained by differences in residual gastric volume. We concluded that the cat duodenum provides a resistance to gastric emptying over and above that generated by the pylorus, and that the duodenal resistance is caused by limitations in duodenal capacity. It is furthermore concluded that the mechanical activity of the isolated stomach and duodenum is affected by the chemical composition of their luminal contents.

Animals↗
PubMed1995

Evaluation of a high sodium-low potassium cold-storage solution by the isolated perfused rat kidney technique.

The isolated perfused rat kidney (IPK) model was used to assess initial renal function after 24 h preservation in 3 different cold storage solutions: EuroCollins (EC), a solution prepared according to the formulation of Belzer's solution (High-K+ UW) and a high Na(+)-low K+ Belzer UW solution (High-Na+ UW). GFR and FRNa were measured after 24 h cold storage in each of the solutions during 60 min, and were compared to values obtained in a control group in which renal function was measured immediately after the kidneys had been harvested. ATP and CP were measured in fresh renal tissue, in kidneys preserved for 24 h in each solution, in control IPK, and in reperfused IPK after they had been preserved for 24 h. Main results showed that preservation in either solution caused a dramatic decrease in GFR and in FRNa within the first 60 min following reperfusion of cold-stored kidneys. However FRNa was significantly higher in the High-Na+ UW group. ATP and CP content were decreased to approximately 10% of basal values in all experimental groups after cold-storage. Normothermic reperfusion of IPK after cold-storage induced a restoration of ATP levels, but CP content decreased further. There was no significant difference in ATP and CP content between cold-storage solutions, nor any correlation between metabolic and functional parameters.

Adenosine↗
PubMed1995

Effects of preservation solutions on cortical and medullary mitochondria of rat kidney.

The mitochondria isolated from cortex and medulla of rat kidneys were examined after storage in either Euro-Collins solution, in Bretschneider's histidine-tryptophan-ketoglutarat solution or in Belzer's University of Wisconsin solution at 25 degrees C or at 4 degrees C for a maximum of 4 to 24 hrs. Independently to the preservation of the solution used, the storage of the kidneys led to a decrease in state 3 respiration and uncoupled respiration as well as to an increase in the rate of state 4 respiration. The decrease in state 3 respiration ran parallelly to a decrease in adenine nucleotides. For the homogeneous protection of the mitochondria as well from the cortex as from the medulla, the Bretschneider's solution had the best preservative effect at a storage temperature of 25 degrees C as shown by the measured mitochondrial parameters. At 4 degrees C storage temperature, the differences in action with the various examined solutions were markedly smaller. However, compared to the other two solutions, the Euro-Collins solution showed a more favourable protective effect on cortical and medullary mitochondria.

Adenine Nucleotides↗
PubMed1994

Storage of pancreatic digest before islet purification. The influence of colloids and the sodium to potassium ratio in University of Wisconsin-based preservation solutions.

The density-dependent purification of islets from several species of mammalian pancreata is improved by prior storage of the dispersed, collagenase-digested pancreas in suitable storage solutions, such as University of Wisconsin (UW) solution. The optimal composition of such solutions, however, is not fully established, although previous investigations have suggested separately that cellular impermeants and colloids are important components. To investigate this issue further, dispersed tissues from 7 porcine and 7 human pancreata were stored in UW or in solutions containing the impermeants lactobionate and raffinose, with either no added colloid or in the presence of the colloids hydroxyethyl starch, dextran 40, dextran 250, or Ficoll 400; hydroxyethyl starch-containing solutions in which the principal cation was sodium, rather than potassium, were also studied. Subsequent purification of islets on continuous linear density gradients of BSA was then assessed by insulin/amylase assay of gradient fractions. Islet purity was slightly reduced using solutions containing impermeants but lacking a colloid, compared with using UW. In the combined presence of impermeants and a colloid, however, islet purity was similar to that obtained with UW, and for porcine pancreata, solutions containing Ficoll 400 or dextran 40 were slightly superior to UW. Purity was not, however, influenced by the sodium to potassium ratio of storage media. In conclusion, impermeants and colloids are both essential components of solutions used to preserve pancreatic tissue before islet purification, findings which may be relevant when designing media for use during other phases of islet isolation, e.g., during collagenase digestion/density gradient purification.

Adenosine↗
PubMed1993

Differential impact of Carolina rinse and University of Wisconsin solutions on microcirculation, leukocyte adhesion, Kupffer cell activity and biliary excretion after liver transplantation.

This quantitative in vivo fluorescence microscopy study investigated the relative impact of an optimized rinse solution (warm Carolina rinse) and that of an established storage solution (University of Wisconsin solution) on various pathomechanisms of hepatic reperfusion injury after cold storage. Syngeneic orthotopic, arterialized liver transplantation was performed in male Lewis rats after 24 hr of cold ischemia (n = 24). The four experimental groups differed according to the type of preservation/rinse solution used: University of Wisconsin solution/albumin rinse (group 1), autologous blood (just external cooling)/albumin rinse (group 2), blood/Carolina rinse (group 3) and University of Wisconsin solution/Carolina rinse (group 4). Hepatic microvascular perfusion, leukocyte accumulation and phagocytic activity of Kupffer cells were assessed by means of intravital fluorescence microscopy 30 to 90 min after reperfusion. Disturbances of microvascular perfusion were most pronounced in group 2, markedly reduced by University of Wisconsin solution (group 1) and Carolina rinse (group 3) and minimized by combined use of University of Wisconsin solution and Carolina rinse in group 4. Intrahepatic leukocyte-endothelium interaction in sinusoids and postsinusoidal venules was found to depend on the application of Carolina rinse before reperfusion rather than the use of University of Wisconsin solution during cold storage. Activation of phagocytosis by Kupffer cells was most pronounced in group 1, intermediate in groups 2 and 3 and not noticeable in group 4. Hepatocellular excretory function as assessed on the basis of total bile flow and excretion of bile acids during the first 90 min after reperfusion was found to be improved by application of Carolina rinse, both after storage in blood or in University of Wisconsin solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1996

[Hypertonic solutions and intracranial pressure].

The properties of the endothelium differ between the brain and the remainder of the body. In most non-CNS tissues the size of the junctions between endothelial cells averages 65 A. Proteins do not cross these gaps, while sodium does. In the brain, the junction size is only 7 A, which is too small to allow crossing by sodium. Investigations with changes in osmotic and oncotic pressure have demonstrated that: (1) reducing osmolality results in edema formation in all tissues including normal brain; (2) a decrease in oncotic pressure is only associated with peripheral edema but not in the brain; (3) in case of brain injury, a decrease in osmolality elicits edema in the part of brain which remained normal; (4) similarly, a decrease in oncotic pressure does not cause an increase in brain edema in the injured part of the brain. The determinant factor of water exchange in the brain is mediated through the osmolality and not the oncotic pressure. The use of hypertonic solutions (Ringer lactate or NaCl) for intravascular fluid resuscitation of patients suffering from hypovolemic head trauma has gained popularity. A research survey in regard with this observation can be summarized as follows: NaCl 7.5% (2400 mOsm/l) is becoming the most popular hypertonic solution because of its favorable systemic and cerebral effects. It improves myocardial contractility, precapillary dilatation, and reactive venoconstriction, and it has a plasmatic expansion factor of 3.8. In regard to the brain tissue, it improves the PO2 and the cerebral blood flow (CBF) as a result of decreasing cerebrovascular resistance. Finally, it reduces the cortical water content of intact blood-brain barrier area. The overall consequence is reduction of intracranial pressure (ICP). Although the homeostasis of the cerebral intracellular compartment remains unknown, it is possible that brain cells are able to resist important osmolar overload. NaCl 7.5%/dextran 70.6% is clinically at this moment the most studied hypertonic/hyperoncotic agent in prehospital emergencies. Its effects on cerebral homeostasis are identical to NaCl 7.5%. However, the addition of a colloid agent has the advantage of prolonging the systemic effects without affecting the brain. The plasmatic expansion factor is 4.5, which is slightly superior to NaCl 7.5%. Mannitol improves CBF by maintaining autoregulation as a result of changes in viscosity and reactive cerebrovascular constriction. It generates an osmotic gradient which reduces the cerebral volume and subsequently the ICP. In the presence of a cryogenic cerebral lesion, its reductive effects on brain water are superior to the hypertonic/hyperoncotic solution. Because mannitol has less spectacular systemic responses than the other solutions, it is not indicated for resuscitation following hemorrhagic shock. In conclusion, it is important to note that hypotension and hypoxemia represent the determinant factors of secondary cerebral insults. Therefore, in the presence of patients with head injury and especially hemorrhagic shock, it is essential to ensure a cerebral perfusion pressure (CPP) of > 80 mm Hg. Hypertonic solutions have gained popularity in these clinical situations because of their combined effects on ICP, mean arterial pressure (MAP) and CPP. However, the therapeutic approach to polytraumatized patients with small intravascular volume (4-6 ml/kg) of hypertonic solutions should not be a substitute for the usual volemic resuscitation technique. The clinical indication for these solutions should be limited to the initial resuscitation maneuvers in traumatized patients. Prolonged use of hypertonic solutions for the purpose of intravascular resuscitation would only contribute to increasing the side effects and eventually counteract the initial beneficial advantages.

Blood Pressure↗
PubMed1995

Compatibility of reduced glutathione (GSH) with different solutions currently used in anesthesia and reanimation.

BACKGROUND: Reduced glutathione (GSH) an antioxidant used for i.v. or i.m. administrations, prepared as powder to be diluted in distilled water just before injection (Tationil 600), could lose its antioxidant properties when added to various infusions currently utilized in anesthesia and reanimation. AIM OF THE WORK: Evaluate in vitro the compatibility of the compound marketed under the trade nome "Tationil 600" with the intravenous infusions in common use in anesthesia and reanimation. MATERIALS AND METHODS: 10 mg GSH (Tationil 600) were added to 10 ml of different solutions: 0.9% saline (I), 5% glucosate solution (II), Normosol-M and 5% glucose (III), 3.5% Emagel (IV), Propofol 10 mg/ml (V), in order to obtain a final solution containing 1 mg og GSH per ml of solution. The different solutions were incubated and aliquots taken at different times and analyzed. RESULTS: GSH in its commercial preparation proved to be compatible with all solutions examined with exception of solution III, because of the interference of sodium bisolfite. CONCLUSIONS: Reduced glutathione (Tationil 600) was compatible with solutions I, II, IV and V, used for i.v. administrations in anesthesia and reanimation, and revealed to maintain its antioxidant properties when studied over a period of 24 hours.

Anesthesia↗
PubMed1998

[Osmolarity of solutions used in nebulization].

Inhaled medications are widely used in patients suffering from bronchial diseases. Beside their pharmacological properties, nebulised solutions have physico-chemical characteristics that can alter bronchial reactivity. Non-isotonic solutions can induce a bronchial hyperresponsiveness and/or a severe bronchonconstriction. Nevertheless, multiple drugs are used for nebulisation despite their unknown osmolarity. The aim of this study was to measure the tonicity of drug solutions commonly used for nebulisation in patients suffering from bronchial disease. Drug solutions were prepared either according to manufacturer recommendations or by diluting the stock in 5 ml of NaCl (0.9%) or H2CO3 (0.14%). Although bronchodilatator solutions (i.e. salbutamol, terbulatine, ipratropium bromide) were nearly isotonic, some drugs prepared for nebulisation had either a very high (e.g. mesna, netilmicine) or a very low (e.g. gomenol, sodium cromoglycate) tonicity. These values may be responsible for bronchoconstriction. Some hypertonic solutions, prepared with drugs such as acetylcytein or netilmycin, are not commercialised for nebulisation but are commonly used for aerosol therapy. In addition, solutions initially isotonic could become significantly hypertonic towards the end of nebulisation. Taken together, these results suggest that non-isotonic solutions should be used with caution specially in patients with bronchial hyperresponsiveness, even when aerosol therapy is prescribed for upper airways.

Acetylcysteine↗
PubMed1992

Comparison of the University of Wisconsin preservation solution and other crystalloid perfusates in a 30-hour rabbit lung preservation model.

The University of Wisconsin solution, which contains a high potassium concentration (120 mmol/L), was evaluated for rabbit lung preservation by comparing it with a modified University of Wisconsin solution with low potassium (4 mmol/L), a low-potassium dextran solution (4 mmol/L), and simple surface cooling. In the first three groups rabbit lungs were flushed in situ with the solution (n = 5 in each group); then the lung-heart block was harvested and stored at 10 degrees C for 30 hours. In the surface cooling group the lungs were harvested without flushing and then simply immersed in saline and stored. For assessment, the stored lung was ventilated with room air and perfused with fresh venous blood at a rate of 40 ml/min for 10 minutes. Assessment of lung function included gas analysis of effluent blood, mean pulmonary artery perfusion pressure, and peak airway pressure. Among these parameters, oxygen tension was most sensitive. Oxygen tension at 10 minutes' perfusion in the modified University of Wisconsin (95 +/- 6 mm Hg) and low-potassium dextran (99 +/- 4 mm Hg) groups was significantly higher than that in the surface cooling (61 +/- 7 mm Hg) and University of Wisconsin (51 +/- 7 mm Hg) groups. There was no difference between the modified University of Wisconsin and low-potassium dextran groups or between the surface cooling and University of Wisconsin groups. We conclude that the low-potassium University of Wisconsin solution is superior to the high-potassium University of Wisconsin solution and that the lactobionate and raffinose included in the University of Wisconsin solution as impermeants do not improve lung preservation in this model.

Adenosine↗
PubMed1999

Adsorption from solutions on synthetic hydroxyapatite: nonaqueous vs. aqueous solvents.

It is useful in restorative dentistry and etiology of bone diseases to know that certain general rules may be derived from a priori considerations of the adsorption of chemicals to synthetic hydroxyapatite (which is the structural prototype of tooth and bone mineral). This article systematically synthesizes the extensive studies on the subject by the author, and rationalizes and extends these rules. Though not a review article, the work of some researchers may not have found an adequate representation here, because they did not determine, in the case of nonaqueous solvents, the reversibility of adsorption; or, in the case of aqueous solvents, the concentration of all constituent ions of the system, thus missing the occurrence of processes other than adsorption. The adsorption of solutes from nonaqueous solvents on hydroxyapatite is mainly regulated by the interplay of hydrogen bonding between adsorbate, adsorbent, and solvent. It does not involve any significant role of ionic nature of the apatite surface, because it is masked by the chemisorbed and physisorbed water. This interplay of hydrogen bonding in conjunction with chemical and structural characteristics of the adsorbed molecules controls their reversibility and the orientation of the adsorbates on the surface. In general, the process may be considered as true adsorption, because no other material exchange process is involved. The "adsorption" of solutes from aqueous solutions generally involves ion-exchange with the apatite surface, and may be affected by the concentrations of potential determining ions (Ca(2+), phosphates, H(+), etc.) in the solution. The solute in aqueous solution may be removed by two other mechanisms, either by formation of a surface complex or by chemically reacting with calcium or phosphate ions to form a new phase that precipitates out of solution. Therefore, the concentration of calcium and phosphate ions in solution should also be monitored to elucidate the mechanism of the process. Adsorption of polymers seems to be determined primarily by their multiple hydrogen bonding, their relative molar mass, and their ability to self-associate. The hydrogen ion concentration plays a decisive role in each one of the above mechanisms.

Adsorption↗
PubMed2000

Rice-based oral rehydration solution for treating diarrhoea.

BACKGROUND: Oral rehydration therapy is used to treat dehydration caused by diarrhoea. However the rehydration solution does not reduce stool loss or length of illness. A solution able to do this may lessen the use of ineffective diarrhoea treatments as well as improve morbidity and mortality related to diarrhoea. OBJECTIVES: The objective of this review was to assess the effects of rice-based oral rehydration salts solution compared with glucose-based oral rehydration salts solution on reduction of stool output and duration of diarrhoea in patients with acute watery diarrhoea. SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group trials register, the Cochrane Controlled Trials Register, Medline, Embase, Lilacs and the reference lists of relevant articles. We also contacted researchers in the field. SELECTION CRITERIA: Randomized trials comparing standard World Health Organization oral rehydration solution with an experimental oral rehydration salts solution in which glucose (20 grams per litre) was replaced by 50-80 grams per litre of rice powder, with the electrolytes remaining unchanged. DATA COLLECTION AND ANALYSIS: Data were extracted independently by a statistician and a clinician. MAIN RESULTS: Twenty-two trials were included. Concealment of allocation was adequate in 15 of these trials. Irrespective of age, people with cholera who were given rice oral rehydration salts solution had substantially lower rates of stool loss than those given oral rehydration salts solution in the first 24 hours. Mean stool outputs in the first 24 hours were lower by 67 millilitres/kg of body weight (weighted mean difference -67.4, 95% confidence interval -94.3 to -41.0) in children, and by 51 millilitres/kg of body weight (weighted mean difference -51.1, 95% confidence interval -65.9 to -36.3) in adults. The rate of stool loss in infants and children with acute non-cholera diarrhoea was reduced by only four millilitres/kg of body weight (weighted mean difference -4.3, 95% confidence interval -9.3 to 0.8). REVIEWER'S CONCLUSIONS: Rice-based oral rehydration appears to be effective in reducing stool output in people with cholera. This effect was not apparent in infants and children with non-cholera diarrhoea.

Adult↗
PubMed2005

Monovalent cations affect the free solution mobility of DNA by perturbing the hydrogen-bonded structure of water.

The free solution mobilities of single- and double-stranded DNA molecules of various molecular weights have been measured by capillary electrophoresis in solutions of constant ionic strength containing a common anion and fifteen different monovalent cations. In solutions with the same ionic composition, the mobilities of different DNA molecules can vary by up to 20%, depending on molecular weight, the number of strands, and the presence or absence of A-tracts, runs of four or more contiguous adenine residues. Importantly, the mobilities observed for the same DNA sample can vary by up to 40% in solutions containing different cations. The mobility differences observed for the same DNA in solutions containing different cations cannot be rationalized by differences in the anhydrous radii or intrinsic conductivities of the various cations, or by the sequence-dependent binding of certain cations to A-tracts. Instead, the observed mobilities are linearly correlated with the average number of water-water hydrogen bonds that are present in solutions containing different cations. The mobilities are also correlated with the viscosity B coefficients of the various cations and with the rotational correlation times frictional coefficients observed for water molecules in solutions containing different cations. Hence, monovalent cations modify the free solution mobility of DNA primarily by perturbing the hydrogen-bonded structure of water, affecting the friction experienced by the migrating DNA molecules during electrophoresis.

Base Sequence↗
PubMed2004

Enthalpy of solution of 1,4-naphthoquinone in CO2 + n-pentane in the critical region of the binary mixture: mechanism of solubility enhancement.

The enthalpy of solution (Delta(solv)H(m)) and solubility of 1,4-naphthoquinone in CO(2) + n-pentane were measured at 308.15 K in the critical region of the binary fluid. In order to study the effect of phase behavior of the mixed solvent on Delta(solv)H(m), the experiments were carried out in the supercritical (SC) and subcritical region of the binary solvent. The density of the mixed solvent in different conditions was determined. The isothermal compressibility (K(T)) of the mixed solvent, and the partial molar volume (V(n-pentane)) of n-pentane in the solution were calculated. It was demonstrated that the Delta(solv)H(m) was negative in all conditions. Delta(solv)H(m) is nearly independent of pressure or density in all the solvents in a high-density region, in which compressibility of the solvent is very small; this indicates that the intermolecular interaction between the solvent and the solute is similar to that for liquid solutions. It is very interesting that Delta(solv)H(m) in the mixed SC fluid differs from the Delta(solv)H(m) in mixed subcritical fluids. The absolute value of Delta(solv)H(m) in the mixed SC fluid is close to that in pure SC CO(2) in the high-density region, and is much lower than that in pure SC CO(2) in the low-density region. In the mixed subcritical fluids, the Delta(solv)H(m) is also close to that in the pure CO(2) in the high-density region. However, at the same density, the absolute value of Delta(solv)H(m) in the binary subcritical fluid is larger than that in pure CO(2) in the high-compressible region of the mixed solvent. The main reason for this is that the degree of clustering in the SC solutions is small at the density in which the degree of clustering is large in the subcritical solutions. It can be concluded that solubility enhancement by n-pentane in the mixed SC fluid is entropy driven. In contrast, the solubility enhancement by n-pentane in subcritical fluids is enthalpy driven. The intermolecular interaction in the SC solutions and subcritical solutions can be significantly different even if their densities are the same.

Carbon Dioxide↗
PubMed2006

Electrokinetic transport of charged solutes in micro- and nanochannels: the influence of transverse electromigration.

The accurate prediction of electrokinetic migration velocity and dispersion is crucial to separating electrophoretically charged solutes in micro- or nanochannels. In this paper, we investigate numerically the influence of transverse electromigration (TEM) on the solute electrokinetic transport in a series of micro- and nanochannels. The TEM, often ignored in previous studies, is demonstrated to significantly affect the solute migration velocity in nanochannels and the electrokinetic dispersion in microchannels. This is because the TEM can force either positively charged solutes into or negatively charged solutes out of the electrical double layer that forms adjacent to the negatively charged channel wall and contains the velocity gradients. Analytical solutions are also derived for characterizing the electrokinetic transport of charged solutes in nanochannels, which has been validated to be in good agreement with the numerical simulation. Moreover, we demonstrate that the proposed analytical formula for the solute migration velocity actually applies to channels of any size.

Electrophoresis↗