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The objective of the present study was to establish a culture of Hyalella azteca that could be used for laboratory toxicity testing in low–ionic strength waters with electrical conductivities of

Impurities in indicator salts can significantly bias spectrophotometric pH determinations. In this work, two purified sulfonephthalein indicators, meta-cresol purple (mCP) and phenol red (PR), were tested for analysis of freshwater pH on the free hydrogen ion concentration scale. These two purified indicators were characterized for the first time under low ionic strength conditions, providing their molar absorption coefficients and dissociation constants along with their temperature dependence from 8 °C to 30 °C. At 25 °C, the infinite dilution constants ( pKIo) were determined to be 8.6606 and 8.0642 for mCP and PR, respectively. The accuracy and precision of the method, evaluated with a variety of buffers with known pH, were found to be +0.0014 pH units and ±0.0022 pH units, respectively (n = 30). The pH values of different freshwater samples were also determined using both indicators. The mCP and PR results were all within ± 0.01 pH units of each other with three out of seven pH differences within ± 0.001 pH units, indicating the high consistency between these two indicator methods. The work presented here is the first parallel comparison with two purified indicators used to determine pH of the same freshwater samples.

Summary The effects of 5 mm l-histidine (l-His) on water-binding capacity, gel strength, thermal gelling properties of chicken breast myofibrillar proteins (MPs) in 1 mm NaCl or 0.6 m NaCl solutions (pH 7.0) were investigated. l-His could significantly increase the solubility and thermal gelling ability of MPs in 1 mm NaCl. l-His at 1 mm NaCl shortened the water relaxation time and decreased the water mobility of MPs gel. l-His promoted the formation of MPs gel structure with small pores and thin strands at 1 mm NaCl. These resulted in the enhanced water retention and weak gel strength of MPs in low ionic strength solution. The water-binding capacity of MPs gels formed in 1 mm NaCl containing 5 mm l-His was equivalent to that with 0.6 m NaCl. The information could offer certain theoretical foundation to apply l-His as sodium salt substitute for developing low-salt meat gelling product with high yield.

Maize cultivars (Zea mays L.) were evaluated for their aluminum (Al) sensitivity using intact plants and excised root tips exposed to 25 μM Al in nutrient solution of low ionic strength and pH 4.3. Aluminum supply increased callose formation and Al concentrations in root tips of intact plants as well as in excised root tips. Using intact plants, differences in Al sensitivity among cultivars could be characterized by Al-induced callose formation, Al-induced inhibition of root elongation, as well as Al contents in root tips as parameters. Significant correlations between Al-induced callose formation and Al contents in root tips (r2 = 0.64**) and inhibition of root elongation (r2 = 0.80***) were found. Excised root tips did not show a significant Al-induced inhibition of root elongation. While average Al-induced callose formation was similar for root tips of intact plants and excised root tips, mean Al contents in excised root tips were up to 1.5-fold higher than in root tips of intact plants after 24 h of Al treatment. Aluminum-induced callose formation as found in excised root tips did neither correspond to Al-induced callose formation nor to inhibition of root elongation of intact plants. The addition of 10 mM glucose to the incubation medium led to a significant increase in the elongation of excised root tips and a 2-3-fold increase in Al-induced callose formation. Staining with triphenyl-tetrazolium-chloride (TTC) revealed increased viability of these root segments. However, these effects of glucose supply did not improve the characterization of the cultivars for Al resistance. The results presented suggest that Al exclusion mechanisms expressed in root tips of intact plants might be non-operational in excised root tips. Therefore, the characterization of maize germplasm for Al resistance using excised root tips appears not to be reliable. Charakterisierung der Aluminium-Empfindlichkeit von Mais-Genotypen an intakten Pflanzen im Vergleich zu abgeschnittenen Wurzelspitzen Die Aluminium (Al)-Empfindlichkeit von Mais-Genotypen (Zea mays L.) wurde an Wurzeln intakter Pflanzen im Vergleich zu abgeschnittenen Wurzelspitzen durch Angebot von 25 μM Al in Nahrlosung mit geringer Ionenstarke und pH 4,3 charakterisiert. Aluminium-Angebot fuhrte sowohl bei Wurzeln intakter Pflanzen als auch bei abgeschnittenen Wurzeln zu vermehrter Kallose-Bildung und erhohten Al-Gehalten. Bei Wurzeln intakter Pflanzen konnten ubereinstimmende Unterschiede in der Al-Empfindlichkeit sowohl durch das Ausmas der Al-induzierten Kallose-Bildung, der Al-Gehalte in den Wurzelspitzen als auch der Hemmung des Wurzellangenwachstums festgestellt werden. Die Kallose-Gehalte waren mit den Al-Gehalten (r2 = 0,64**) und mit der Hemmung des Wurzellangenwachstums (r2 = 0,80***) signifikant positiv korreliert. Bei abgeschnittenen Wurzelspitzen hemmte Al-Angebot das generell geringe Wurzelwachstum nicht. Wahrend die Al-induzierte Kallose-Bildung vergleichbar zu intakten Wurzeln war, waren die Al-Gehalte nach 24 h Al-Angebot um den Faktor 1,5 erhoht. Aluminium-induzierte Kallose-Bildung in abgeschnittenen Wurzeln war nicht korreliert mit der Kallose-Bildung und der Hemmung des Wurzellangenwachstums bei intakten Pflanzen. Zusatz von 10 mM Glukose zum Inkubationsmedium fuhrte zu einer signifikanten Forderung des Langenwachstums und einer 2-3fach erhohten Kallose-Bildung bei abgeschnittenen Wurzeln. Anfarbung der Wurzelspitzen mit Triphenyl-Tetrazolium-Chlorid (TTC) zeigte eine stark verminderte Vitalitat 24 Stunden nach dem Abschneiden. Der Glukosezusatz verbesserte jedoch nicht die Klas-sifikation der Genotypen nach Al-Empfindlichkeit. Die Ergebnisse weisen darauf hin, dass der fur Al-Resistenz in-takter Pflanzen verantwortliche Mechanismus der Diskriminierung von Al von der Aufnahme in die Wurzelspitzen in abgeschnittenen Wurzeln beeintrachtigt ist. Daher ist ein Screening von Mais-Geno-typen auf Al-Resistenz mit abgeschnittenen Wurzelspitzen nicht zuverlassig moglich.

We used air operating atomic force microscopy (AFM) to study several morphological modifications of human erythrocytes, artificially produced by addition of exogenous agents including phospholipids, low ionic strength media and drugs. Most experiments were performed on unfixed samples to avoid treating red blood cells (RBCs) with chemical agents that can, in principle, induce morphological alteration. After detailed quantitative AFM characterization, the artificially produced abnormally shaped RBCs were compared with cells that occur with high incidence in blood pathologies. This morphological approach suggests a new strategy to describe and understand the biochemical and/or mechanical modifications responsible for the underlying pathologically induced changes and prove AFM to be a suitable tool to study erythrocyte deformation.

CR1 and CR2 are expressed as associated proteins on the B-lymphocyte surface. To investigate their respective contributions to the internalization of C3 fragments, transfected murine fibroblasts expressing human CR1, CR2, or both CR1 and CR2 were produced. CR1- and CR1–CR2-expressing cells bound C3b and C3b-dimer whereas CR2- and CR1–CR2-expressing cells bound iC3b and C3de. In all cases, maximum binding was achieved at low ionic strength. CR1–CR2-positive cells internalized two- to threefold more C3b and 1·5-fold more iC3b than CR1- and CR2-single-positive cells, respectively. Internalization of the anti-CR1 antibody J3D3, or C3de was at the same level, in both double-transfected and single-transfected cells. Furthermore, the internalization of C3b dimer by CR1–CR2 cells was impaired in the presence of OKB7, an anti-CR2-blocking antibody, but it was not altered in CR1 cells. Taken together, these findings suggest that CR1 and CR2 collaborate to internalize C3b and iC3b proteins. We suggest that the induction of conformational changes of the ligands enhances their binding to both receptors.

The influence of an external radial electric field (E(R)) on electroosmosis in capillary electrophoresis was studied theoretically. Based on a Stern-like model, three basic equations were deduced, with only two unknown parameters of delta and psi(d) where delta is the distance between the flowing shear interface and the tube wall, while psi(d) is the potential at the starting point of diffuse layer. The new equations reveal that, to effectively regulate the electroosmosis at E(R)

The sensitivity of the low ionic strength solution antiglobulin test (LISS-AGT), polyethylene glycol antiglobulin test (PEG-AGT), low ionic strength solution solid-phase anti-globulin test (LISS-SPAT), gel low ionic strength solution antiglobulin test (GEL-LISS), and gel papain test (GEL-PAP) was compared in titration studies of 460 sera containing identified IgG alloantibodies. The GEL-PAP was 100% sensitive to detect Rh antibodies, whereas the PEG-AGT was the most sensitive to detect Kell, Duffy, Kidd, Ss, and rare blood group antibodies. The better performance of PEG-AGT was especially obvious with Kell, Duffy, and Ss antibodies (S = 100%). When the sensitivity of the LISS-AGT, PEG-AGT, GEL-LISS, and GEL-PAP was evaluated in different routines, the GEL-LISS showed to be more sensitive than PEG-AGT in the detection of clinically significant antibodies. These discrepant results showed that the performance of a technique may change when it is applied as a routine. © 1996 Wiley-Liss, Inc.

Protein isolates prepared from acid whey concentrate and cheese whey concentrate, and β-lactoglobulin were studied. Turbidity of samples was measured using a 96-well microplate and a microreader. This method allowed many (>100) small samples (< 250 μL) to be treated at the same time. At low ionic strength and at neutral to alkaline pH, samples were transparent after heating. Transparent gels could also be prepared in this region with a small amount of NaCl.

Although the charge balance for a single chemical analysis of a water's electrolytes is not a reliable gauge for the accuracy of that analysis, the percent charge-balance error (%CBE) becomes more credible as a means for evaluating analytical technique when applied to groups of analyses. Just how good are charge balances for chemical analyses of potable ground and stream waters in mainline geological journals? Starting with each journal's first volume, a search found 68 articles in six journals (Appl. Geochem., Chem. Geol, Geochim. Cos. Acta., Ground Water, J. Hydrol, and Water Resources Res.) that had what was deemed to be “complete” analyses of individual samples' major ions. Analyses of brines and hydrothermal solutions were excluded as were “composite” averages. A total of 1,062 %CBEs were computed and tabulated, and the average was 3.99%$ 6.56 (1σ). The average %CBE (by journals) ranges from 1.55% to 9.34%. Quality of %CBE is slightly better for articles published after 1970. Not surprisingly, low ionic strength samples are prone to charge-balance errors > 10%. Of the 1,062 charge balances calculated, 612 were positive and 450 were negative. Eight of the 68 articles had analyses that were evenly balanced between positive and negative CB errors. There are 21 articles in which the majority of analyses had negative charge-balance errors. Thus a clear majority (39) of articles had analyses in which there were more positive than negative charge-balance errors. Systematic error is likely for situations where the analyses in an article are predominantly positive or predominantly negative. The likely reason for the former occurrence is lab determination of alkalinity from the nonacidified field aliquot. Failure to filter samples may cause the latter situation—especially in carbonate terranes. Systematic laboratory errors involving salt standards and dilutions can also yield charge-balance errors for a suite of analyses that are skewed to either positive or negative errors. The care with which the analyst did his/her job may also impact charge-balance errors.

Complexes of polyanions and polycations that precipitate at low ionic strength, [I], from aqueous solutions become soluble when [I] is increased. The critical ionic strength for resolubilization [I]crit has been determined for various combinations of polyanions and polycations. [I]crit depends on the chemical nature of the polyelectrolytes. Provided the difference in [I]crit is sufficiently large, different polyelectrolytes of the same charge state can be separated via selective precipitation with the aid of an appropriate polyelectrolyte of opposite charge state. The method has been exemplified by separating albumin from polyphosphate via precipitation as polyelectrolyte complex with poly(N-ethyl-4-vinylpyridinium bromide). The process was performed at pH 8, where albumin acts as polyanion. Polyanionen- und Polykationenkomplexe, die sich bei geringen Ionenstarken [I] aus wassrigen Losungen abscheiden, werden bei Erhohung von [I] wieder loslich. Die kritische Ionenstarke, [I]crit, bei der sich die Komplexe erneut losen, wurde fur verschiedene Polyanion/Polykation-Kombinationen bestimmt. [I]crit hangt von der chemischen Konstitution des Polyelektrolyten ab. Vorausgesetzt, das sich die kritischen Ionenstarken genugend voneinander unterscheiden, konnen verschiedene Polyelektrolyte mit dem gleichen Ladungszustand durch selektive Abscheidung mit Hilfe eines geeigneten, entgegengesetzt geladenen Polyelektrolyten getrennt werden. Diese Methode wird am Beispiel der Trennung von Albumin von Polyphosphat als Polyelektrolytkomplex mit Poly(N-ethyl-4-vinylpyridiniumbromid) veranschaulicht. Die Abtrennung wurde bei pH 8 durchgefuhrt; dabei liegt Albumin als Polyanion vor.

The ability to drive catalytic processes when dc voltages are applied to low ionic strength dispersions has been demonstrated for the selective partial oxidation of propene at 0 °C in an aqueous dispersion of PdII–CuII supported on Y zeolite where the primary partial oxidation product can be either acetone or propylene oxide depending on the nature of the dispersed solid; in the absence of the applied electrifying force no product forms and in the absence of the molecular catalyst no selective oxidation occurs.

Protein fractions [high ionic strength soluble (HIS), low ionic strength soluble (LIS) and insoluble (IN)] and myosin percentage of beef skeletal tissues were varied in model system frankfurter batter formulations by substitution of lung, heart and spleen to investigate changes in stability and textural properties. Percentage myosin and HIS proteins were positively correlated to reheat yield and apparent strain and stress at failure in the cooked batters. The quantity of LIS proteins was negatively correlated, whereas the quantity of IN proteins were not highly correlated with the batter parameters evaluated. Properties examined in protein gel and batter model systems were highly correlated. Results suggest that the yield and texture of frankfurters might be improved by adjusting the type and quantity of meat in a formulation to achieve minimum quantities of HIS protein and myosin.

Gelation properties were evaluated on high ionic strength soluble (HIS) proteins alone and in combination with low ionic strength soluble (LIS) or insoluble (IN) proteins from beef skeletal, heart, lung and spleen tissues. Apparent stress and strain at failure were greatest in skeletal HIS 6% (w/w) protein gels, followed by heart, lung and spleen. Expressible moisture was greatest in lung HIS protein gels. Microstructures of 6% (w/w) HIS protein gels from skeletal, cardiac and lung tissues were fibrous, while lung HIS protein gels had a globular matrix. Substitution of LIS or IN proteins into HIS protein gels altered expressible moisture, gel microstructure and apparent stress and strain at failure.

Thin filaments were prepared from rabbit and beef skeletal muscle with three different procedures, both at high and low ionic strength. Nebulin was always found to be associated with the myosin fraction and was always absent from the thin filament fraction.

Egg white was dialyzed against distilled water or diluted with water, and the precipitates formed were removed by centrifugation. The supernatant gave a transparent gel after being heated at an acidic pH (2–4). At other regions of pH, except for the highly alkaline region, the gel or suspension was turbid upon heating. Insufficient centrifugation of the dialyzed egg white or the addition of NaCl to the supernatant after centrifugation resulted in a turbid gel on heating at even acidic pH. The removal of the slight precipitate formed at low ionic strength and the maintenance of low ionic strength during heating were both necessary for production of a transparent gel.

Two low ionic strength-dependent autoagglutinins were studied and found to have anti-Pr1 specificity. This specificity was determined by studies with enzyme-treated and neuraminidase-treated human red blood cells (RBCs), animal RBCs and chemically-modified sialoglycoproteins, all suspended in a low ionic strength solution (LISS). Both IgM complement-binding cold agglutinins had a wide thermal range and caused in vitro hemolysis of some LISS-suspended RBCs at 37 degrees C. Compatible blood was found for these patients by using techniques that did not employ LISS.

A study of roll-up in a model oily-soil detergent system has shown that the addition of a second surfactant in a minor amount to an effective detergent can either enhance or inhibit roll-up. Which effect takes place depends on the relative surface activity of the components, the levels used, and, for ionic surfactants, the electrolyte content. Addition of anionic surfactants can reduce the performance of an effective nonionic under low ionic strength/low hardness conditions. However, in high ionic strength/high hardness solutions, where the anionic is effective, the situation is reversed and addition of the nonionic component can, in some cases, reduce the rate of roll-up. Roll-up behavior appears to be controlled by the oil/ water interfacial tension. When the interfacial tension increases above a critical value, roll-up is inhibited. A theory that has been used to predict surface tensions of mixtures is also useful in estimating oil/water interfacial tensions. The theory provides an understanding of why the interfacial tension can rise when mixed micelles are formed.

The investigation presents evidence for the value of suspending red cells in a low ionic strength medium for elution experiments since this has the effect of increasing the uptake of antibodies by the red cells. In addition it has been shown that for the titration of low affinity antibodies, and also of eluted antibodies, the combining capacity of which may be impaired through the elution process, it is an advantage to use a LISS-enzyme (papain) technique.

A method for preparing dry powders from fish muscles is described. The muscle dry powders (MDP) were extracted with low ionic strength buffer and compared with sarcoplasmic extracts of raw muscles by isoelectric focusing on ultra-thin layer (100 μm) polyacrylamide gels. The protein patterns of MDP extracts corresponded to the patterns of the acidic proteins of raw muscle extracts. Because of the species specificity of the patterns, MDP can be used as reference material for fish species identification. The acidic proteins remained extractable after storage of MDP for several months at room temperature.

Optical rotation data indicate that xanthan can exist both in an ordered and a disordered conformation. Using molecular weights obtained from light scattering measurements and contour length distributions obtained from electron micrographs, we find that a native, filtered xanthan exposed to low salinity (< 10−4M NaCl) and subsequently returned to 0.1M NaCl has a highly elongated structure with a mass per unit length of 1950 ± 200 Dalton/nm. Our data thus suggest that the ordered conformation of this xanthan is double stranded. We find that native, filtered xanthan in 0.1M NH4Ac has a nearly similar structure, but exists in part as aggregates of varying shape and size. Electron micrographs of these xanthans in 10−4M NH4Ac (the disordered conformation) display a mixture of species ranging from unaggregated single- or perfectly matched double-stranded species, to double-stranded chains branching into its two subunits as well as double-stranded chains with different degrees of mismatching. This study suggests that the perfectly matched antiparallel or parallel double-stranded chain constitutes the lowest free energy state of the ordered conformation of xanthan in dilute aqueous solution.

C4 sucrose/low ionic strength (LIS)-coated red blood cells (RBC) are excellent for the detection of the previously 'nebulous' antibodies, anti-Chido and anti-Rodgers, as well as for serum/plasma typing of these antigens by an inhibition technique. By enzyme treatment of such cells, it is confirmed that the Ch and Rg antigens reside on the C4d part of the C4 molecule. Freshly taken RBC from normal individuals were examined with a sensitive Auto-Analyzer technique with anti-Chido, anti-C4 and anti-C3 sera. All normal RBC were shown to have C4d and C3d components on their surface. The technique was also very sensitive for the detection of the Ch antigen, which was detected on the RBC of all Chido-positive individuals, and which did not show great variation in strength by this method. The mode of in vivo C4 fixation on normal RBC seems to be different from the fixation in LIS or by RBC antibody-mediated activation.

Manual hexadimethrine bromide (Polybrene) tests (Polybrene in low-ionic medium) were used in parallel with manual low-ionic-strength solution (LISS) procedures for the routine testing of patient samples referred to a general hospital blood bank. Of 5646 consecutive sera tested, 5167 (91.5%) did not react with either technique; 320 sera (5.7%) reacted in both methods. The Polybrene technique detected 63 antibodies which did not react in the LISS methods. One hundred sera did not react in the Polybrene test, but did react in the LISS methods. Sera showing discrepant results between the two methods were further tested in a reference laboratory. Polybrene tests appeared to be better in avoiding reactions due to clinically nonsignificant antibodies. The LISS methods, however, appeared to be more sensitive in detecting antibodies of potential clinical significance.

Phenylalanyl-tRNA and seryl-tRNA synthetase protect strongly through not completely their cognate tRNAs against nuclease attack, as had been shown previously. In an investigation of the mechanism of protection it was demonstrated that the low susceptibility of phenylalanyl-tRNA-synthetase · tRNAPhe complexes to nucleases is due to free tRNA present in equilibrium with synthetase. The equilibrium can be shifted by an excess of synthetase or by dilution of the complex. It therefore appears that synthetase competes with the nuclease for free tRNA. Degradation of the complex is low, however, because under the conditions of partial digestion the synthetase has a greater affinity for the tRNA than does the nuclease. Fragmented tRNAs, as they are formed during partial nuclease digestion, bind to synthetase to different degrees. tRNAPhe with a lesion in the dihydrouridine loop binds very poorly whereas a nick in the anticodon loop reduces the strength of binding to a much lesser extent. In a systematic study of the stoichiometry of protection it was confirmed that under standard conditions one phenylalanyl-tRNA synthetase protects one tRNAPhe and one seryl-tRNA synthetase two tRNASer molecules against nuclease attack. Under certain conditions, however, (concentration of the complex higher than 10 μM, or alternately in buffers of low ionic strength) it is observed that phenylalanyl-tRNA synthetase binds up to 1.6 molecules tRNAPhe. In the serine system, these special conditions do not affect the binding properties of seryl-tRNA synthetase.

Emptying of homogenized segments of skeletal muscle cells in solutions of low ionic strength was directly related to actomyosin content and inversely to content of nucleotide pyrophosphate. Segments from muscle which had undergone thaw rigor, had low nucleotide pyrophosphate and high actomyosin content but did not empty. Glycerinated muscle cell segments, which also had low nucleotide pyrophosphate and high actomyosin contents, were incapable of emptying until the Z-line was extracted. Treatment with ATP, which dissociated actomyosin, prevented emptying even after the Z-line had been removed. It is concluded that both actomyosin formation and Z-line disintegration are required before emptying of muscle cell segments will occur.

Electron microscopy of negatively stained samples indicates that caldesmon induces polymerization of Gactin into filaments. Polymerization takes place in a very low ionic strength solution and is accompanied by an increase of intensity of fluorescence of G-actin labelled with N-(1-pyrenyl)iodoacetamide. The effect of caldesmon is abolished by calmodulin in the presence of Ca2+

Steroid-receptor complexes formed in concentrated cytosol at low temperature, low ionic strength and neutral pH are unable to bind to nuclei. Various procedures are known to promote their ‘activation’. In the present work it is shown that an increase in temperature only enhances the rate of the reaction whereas no change in the equilibrium between activated and non-activated complexes is observed. On the contrary an increase in ionic strength or pH, as well as a removal of a low-molecular-weight inhibitor, not only accelerate the reaction but also increase the concentration of activated complexes at equilibrium. Using two steroids differing 3-fold in their affinity for the receptor, no difference was seen in the effect of the bound steroid on receptor activation. When combining various activation procedures it was observed that they acted independently of each other and additively. In all cases they retained their property of either modifying only the rate of the reaction or both its rate and equilibrium. Using changes in pH, it was also possible to induce shifts in the equilibrium between activated and non-activated complexes. After activation at pH 6.5, a first equilibrium was attained. When the pH was increased to 8 the equilibrium was displaced towards higher concentrations of activated complexes. A lowering of the pH resulted in a reversal of steroid-receptor complexes from the activated to the non-activated state. To clearly establish that this was not due to irreversible damage of the receptor, which would render it unable to bind to nuclei, it was shown that the complexes which had reverted to the non-activated to the non-activated state were still susceptible to activation. Regulatory events may thus exist which, for a given level of hormone and receptor, modulate the concentration of activated steroid-receptor complexes.

This study was carried out to determine the effects of postmortem storage time, temperature and pH on myofibrillar proteins of red and white muscle. Myofibrils were isolated from (1) the red and white portion of semitendinosus muscle postmortem stored at 2°C and (2) at-death red and white portions and suspended and stored in unbuffered 0.15M KC1 at 2°C and in buffered 0.15M KC1 (pH 5.5 and 7.0) at 2° and 25°C. To determine the effect of storage conditions on myofibrillar proteins, ATPase activity was assayed at different ionic strengths and with different modifiers. Assays of myofibril ATPase activity from postmortem muscle showed that (1) myofibrils from the white portion had greater ATPase activity than those from the red portion, (2) Ca2+-modified activity from both portions increased and (3) Mg2+ -EGTA-modified activity increased from the white portion, but remained unchanged from the red portion, during postmortem storage. These changes could be due to modifications of the regulatory protein components of muscle by calcium-activated factor activity. For those myofibrils isolated from at-death muscle and incubated under simulated storage conditions, a precipitous decrease occurred in Ca2+ -and Mg2+-(low ionic strength) and Ca2+- and EDTA-(high ionic strength) modified ATPase activity of myofibrils stored in 0.15M KC1, pH 5.5, at 25°C. Otherwise, little change occurred in these activities under other simulated conditions of storage (i.e., 2°, pH 5.5 and 7.0; and 25°, pH 7.0) with the exception that EGTA modified activity (indicates loss of Ca2+ sensitivity) increased from the white portion at 25° and 2°C, pH 7.0, and from the red portion at 25°C, pH 7.0. Hence, a high storage temperature of 25°C has more detrimental effect on the integrity of myofibrillar proteins, as measured by changes in ATPase activity, than does a low pH of 5.5, or fiber type.

— The multiple forms of acetylcholinesterase found in the electric organ of the eel Electrophorus electricus have been fractionated by differential solubilization from an ammonium sulfate precipitate by means of a column elution procedure (King, 1972). This procedure cleanly separates ‘native’ forms from ‘degraded’ forms, and subsequent sedimentation reveals three native and two degraded forms. All three native forms, in distinction to the degraded ones, are insoluble at low ionic strength and are shifted to higher sedimentation constants by limited collagenase treatment. These results suggest that the long (500 A) tail seen previously on the native forms of this enzyme (Dudaiet al., 1973; Riegeret al., 1973a, b) may contain collagen.

A solid-phase low-ionic strength salt antiglobulin test (LISS-SPAT) has been developed using a micro-plate coated with dried sera as a solid phase. Before coating, the in vitro C3d fragment generation was activated by adding heat-aggregated immunoglobulin. The LISS-SPAT was compared with low-ionic strength conventional antiglobulin test (LISS-AGT) and also with a test using polybrene or papain microplates. When detecting the IgG and IgM antierythrocyte antibodies the reaction was developed in the same way in LISS-SPAT and LISS-AGT. In routine work, the LISS-SPAT provides a fast, reliable, handy and inexpensive screening of antibodies. This method appears to be an additional method to the papain and polybrene tests in microplates.

The sensitivities of manual low-ionic hexadimethrine bromide (Polybrene, LIP) and low-ionic Polybrene indirect antiglobulin tests (LIPAT) were compared with those of a manual low-ionic-strength indirect antiglobulin test (LISS) by using a commercial Polybrene kit. One hundred antibodies were coded, titrated, and tested in parallel. LIP did not detect 36 antibodies: 31 anti-K, two anti-E, two anti-Fya, and one anti-Jka. LIPAT did not detect seven anti-K, two anti-E, and two anti-Jka. The combination of LIP and LIPAT did not detect two anti- E that were reactive only in a two-stage enzyme test and seven anti-K that had titers of 2 or lower by LISS. LISS detected all antibodies except for the two enzyme-reactive anti-E. There were no significant differences in the titers of 63 percent of the antibodies studied. For 54 percent of the antibodies in the Kell system, LISS produced significantly higher titers; for 25 percent of antibodies in the Rh system, LIP did so. The poor sensitivity of the Polybrene kit for anti- K makes it unsuitable as a primary method for antibody screening.

The sensitivity of the indirect Coombs' test was investigated using saline, albumin, or low ionic strength (LIS) in the incubation phase and an incubation time varying from 5 to 120 min. Titration of 41 antibodies showed that LIS always resulted in a higher or almost the same mean scores as the other solutions after the same incubation time. The maximum mean score was always higher with LIS than with saline and was reached after a shorter period of incubation, only 20--40 min even with the weakest antibodies. With LIS, a longer incubation time than 40 min resulted in a sudden decrease in mean score. The maximum mean score using saline or albumin was reached after 40--60 min incubation. The same mean score was obtained after only 15--20 min, when LIS was used. Albumin gave only slightly higher mean scores than saline.

Red blood cells (RBC) stored without plasma in a neomycin, low ionic strength medium at 4 degrees C in excess of 24 h show alterations in antigen reactivity. There is a loss of protease-sensitive RBC antigens and a protease-type increased IgG saline agglutinability of Rh antigens that is associated with increased binding of 125I anti-D. Both the serological findings and the alteration in RBC membrane polypeptides are consistent with protease modification of the membrane due to contamination of the RBC by leukocytes. Neomycin, low ionic strength or leukocytes alone or in dual combination do not produce the observed changes in antigen reactivity. The role of neomycin and low ionic strength in this phenomenon and implication for quality control of reagent RBC used for antibody detection and identification are discussed.

An EDTA-containing, low ionic strength medium, pH 5.1, can be used for incubation of blood to obtain coating of red blood cells with C4 or C3. The coating achieved depends on incubation temperature (4 or 37 degrees C) and on whether or not CaCl2 or MgCl2 is added to the medium. The optimal concentration of EDTA appears to be 2 mM under the present conditions. This is equimolar to the final concentration of the added CaCl/MgCl2. The choice between CaCl and MgCl2 depends on whether blood without anticoagulant or ACD blood is employed. Coated cells keep satisfactorily for 5 weeks at 4 degrees C in Alsever's solution as well as after freezing and thawing. C3-coated cells can be converted to C3d-coated ones by incubation in normal, compatible, EDTA-containing serum at 37 degrees C.

The cross-sectional radius of gyration of the deoxyribonucleoprotein (DNP) threads was measured by small-angle X-ray scattering in a wide range of ionic strengths (from 0.0005 to 2 M NaCl). For DNP in a solution of low ionic strength, this value is 30 A. The increase of ionic strength results in partial deproteinization of DNP, while the cross-sectional radius of gyration varies from 25 A for DNP in 0.7 M NaCl to 10 A for DNP in 2 M NaCl. It is suggested that gradual deproteinization by the increase of NaCl concentration causes conformational changes, which are associated with the alteration of the DNP superstructure. The data are interpreted on the basis of the superhelical model of DNA packing in DNP; however, the coexistence of superhelical and unfolded regions in the DNP structure is also a possibility.

Storage of green beans at 5°C or -4°C significantly affected the distribution of peroxidase fractions. Activity of the soluble peroxidase fraction, extracted with a low ionic strength buffer, decreased while the ionically bound peroxidase fraction extracted with 1M sodium chloride increased with time. This behavior was particularly noticeable at -4°C. The covalently-bound fraction, extracted after treatment with cellulase and pectinase, remained constant during storage at all temperatures. Storage at -40°C had no effect on the distribution of the peroxidase fractions. The relative concentrations of isoperoxidases present in each peroxidase fraction changed with storage time; however, no new isoperoxidases appeared and none disappeared as a result of the treatments applied.

Ultracentrifugal analysis was used to study aggregation of 7S globulin induced by ultrasonic treatment, of water extracts from defatted soybean flakes. In pH 7.6, 0.5 ionic strength buffer, aggregated 7S proteins sedimented as 40–50S species and represented 25–40% of the total proteins. Aggregates also existed at low ionic strength, but dialysis at 0.5 ionic strength caused additional aggregation of sonically modified 7S proteins. After exposure to 0.5 ionic strength, aggregates were stable to subsequent changes in ionic strength with one exception; some reversal of aggregation occurred when samples were dialyzed against water. Aggregates exhibited highest stability at pH 6.5–6.8 and were stable at room temperature for 9 hr or more. Sonic-induced aggregation of 7S proteins resembles the phenomenon observed on heating water extracts at 80°C.

A heat-induced transparent gel from egg white was prepared at low pH and low ionic strength by a one-step heating method. The addition of NaCl to the egg white formed a turbid gel on heating. Egg white, first diluted with water, gave a transparent solution upon heating of this mixture. The solution formed a transparent gel when heated with NaCl up to a concentration of 0.3M for a second time. The transparent gel obtained at 150 mM NaCl was more firm and less adhesive than the turbid gel prepared by the one-step heating method at the same pH, protein concentration, and NaCl concentration.

The pH and acidity of precipitation are difficult to measure accurately because of the low ionic strength of the samples. Use of measured pH to estimate hydrogen-ion concentration may err by as much as 50% if activity coefficients, junction and streaming potentials, and non-Nernstian behavior of the electrode system are ignored. The magnitude of the individual errors is assessed and procedures for measuring pH and acidity to reduce the total error to +-5% are recommended.

The low ionic strength solution (LISS) of Low and Messeter was compared with both the automated low ionic strength Polybrene and the manual IDAT techniques. A five minute incubation with the LISS was sufficient to detect all significant antibodies. By extending the incubation period to 15 minutes it was possible to increase the sensitivity of the reaction (as measured by titer) beyond that of either of the other methods. This LISS procedure has enabled us to greatly extend the applications of a “standby procedure” for elective surgery. In this procedure routine crossmatching is not done. Rather, the blood is placed on standby and if required, transfusion is provided by using the LISS. In one general hospital this resulted in the reduction by 1,600 units of unnecessary crossmatches and an increase of 10 per cent in the total blood utilization rate over a nine-month period.

Three different techniques of antibody screening of donor bloods were sequentially evaluated. Group I (16300 donors) was a standard saline-albumin-AHG technique utilizing polyvalent serum, including incubation at room temperature. In Group II (26,243 donors), incubations (including room temperature) were performed in I. ISS, and monovalent anti-IgG serum was used. For Group III (15,840 donors), the room temperature incubation was not used for the LISS-IgG method of Group II. The three methods were comparable in terms of detection of clinically significant antibodies, while in Group III the detection of clinically nonsignificant antibodies was eliminated. Cost analysis indicates that for a donor center processing approximately 50,000 units per year and willing to prepare its own LISS solutions, conversion to LISS-IgG could produce a savings of between $5,000 and $8,000 per year. LISS-IgG is thus a sensitive and economical technique highly recommended for the donor center committed to manual donor antibody screening.

The Raman and infrared spectra of poly(L-lysine) and poly(DL-lysine) in solution are reported and the effects of various salts are investigated. The results demonstrate that α-helix formation in solution is induced by specific salts and the spectral data support the hypothesis of regions of local order for poly(L-lysine) in aqueous solutions of low ionic strength.

Summary Adsorption, of the herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) on an iron oxide, goethite, was studied in aqueous suspensions as a function of solution pH, ionic strength of the medium, and initial 2,4-D concentration. The 2,4-D anion was reversibly adsorbed on positively charged goethite surfaces, maximum adsorption being observed near the pKa of 2,4-D (2.73) and at low ionic strength. Within certain levels of adsorption (5–22 mg 2,4-D adsorbed/g goethite) the complex became hydrophobic and floated to the liquid surface. This flotation effect disappeared on further adsorption. It is suggested that adsorbed 2,4-D anions are orientated with their hydro-phobic aromatic ends directed towards the solution, the carboxyl groups being weakly bound to positive sites on the oxide surface. At high levels of adsorption, some of the anions are orientated in the opposite direction by π–π interaction, with the first adsorbed layer and the surface reverts to its hydrophilic nature.

A variety of phages including the T-phages [ 1, 2] P22 [3] and k [4] lose infectivity when exposed to ele- vated temperatures (50-60 °) particularly in low ionic strength medium or medium containing chelating agents. Heating also releases native DNA molecules from phage particles and for phages T7, SP-8, osaka 1 and a the DNA was shown to be released as unbroken molecules [4-6]. Since heat inactivation is a simple and rapid method it may offer advantages over those commonly used for extracting DNA from phage par- ticels. This paper reports studies undertaken to investi- gate the generality of heat inactivation as a method for extracting high molecular weight phage DNA and to extend the physical characterisation of heat released DNA molecules. The results show that for phages T1, T2, T3, T4, T7 and P22 heat inactivation of the particles was accompanied by the release of native DNA which in all cases consisted of unbroken mole- cules. Furthermore, the heat released DNA molecules from T2 and T7 had intact shlgle strands and a buoyant density identical to that of homologous DNA extracted with phenol.

The study of the haemocyanin of Pila leopoldivillensis by means of zone electrophoresis on cellulose acetate has shown that its dissociation is favoured by lowering of the ionic strength. These results were confirmed and extended over a larger range of pH and ionic strength values by means of light scattering measurements. An interpretation of the results is given in terms of ionic equilibria. The type and the number of charged groups involved in the dissociation into halves and into tenths are proposed.

SUMMARY— Changes in extractability of the proteins associated with the fragmentation phenomenon of myofibrils in chicken pectoral muscle were studied. The results indicate that the protein fractions extracted by neutralized water from muscle residue. from which water-soluble proteins have been washed out, increase in post-rigor muscle. The extracts from pre- and post-rigor muscle were fractionated with ammonium sulfate into two fractions: the fraction precipitated by 1.7 M ammonium sulfate (Fr.1) and the supernatant (Fr. 2). Depressing effect on the onset of ATP-induced superprecipitation of trypsin-treated myosin 6 which was initially present in Fr. 2 from pre-rigor muscle decreased to a great extent in that from post-rigor muscle, whereas promotive effect on gelation of F-actin and superprecipitation of the myosin 6 which was little in Fr. 1 from pre-rigor muscle appeared in that from post-rigor muscle. It is proposed that an increasing amount of protein which indicates α-actinin activity is released along with the destruction and final dissolution of the Z-line structure during postmortem storage of chicken pectoral muscle.

(1) Muscle and liver aldolase from rabbit are reversibly inactivated in 4M urea at pH 7,6, without being split into sub-units. At the same pH value muscle aldolase, but not liver aldolase, dissociates into three sub-units, if the ionic strength is increased by the addition of NaCl to a final concentration of 0,2M. At pH 5,5 and low ionic strength (in the absence of NaCl) both aldolases dissociate into sub-units.