Large Molecular Weight Fraction Research Articles

Insulin Degradation by Liver Cell Membranes*

Liver cell membranes actively degrade insulin, but the mechanism for this process has not been established. Exposure of [125I]iodoinsulin for various times to a liver cell membrane preparation enriched in blood sinusoidal surfaces resulted in the generation of labeled products of varying sizes. Separation of these products on a molecular sieve column demonstrated a progressive decrease in 125I-labeled material eluting in the insulin peak and an increase in both larger and smaller molecular weight materials. The latter could be separated into at least three distinct peaks. In addition, the material eluting in the insulin peak had a decreased immunoprecipitability, suggesting that this peak was also heterogeneous. The 125I-labeled material extracted from the membranes eluted from the molecular sieve column predominantly in the void volume and in the insulin peak. There was an increase with time in the larger molecular weight fraction. The liver membrane insulin-degrading activity was characterized by polyac...

Hydrogen uptake and methylene blue reduction activities of hydrogenase in Azotobacter agile.

The Tritium (T) uptake method for detecting hydrogenase (Hase) was applied to measure the Hase activity of aerobic nitrogen-fixing bacterium Azotobacter agile. The cell-free extract of this bacterium contains the ATP-stimulated T-uptake activity, and this activity was separated from the nitrogenase activity. In the supernatant obtained by centrifugation at 20,000 × g for 30 min, this ATP-stimulated T-uptake activity existed mainly in large molecular weight fraction and was distributed to precipitate at 184,000 × g for 1 hr. After this ultra-centrifugation, the distribution patterns of methylene blue (MB) reduction and T-uptake activities were significantly different from each other, and MB reduction activity remained much more in the supernatant. The Hase activity detected by both T-uptake and MB reduction was mainly in the particle fraction precipitated at 20,000 × g for 30 min from the cell-free extract. When the activities of the praticle fraction were solubilized with Triton X–100, the ATP-stimulated ...

Glucosylphosphoryldolichol: Role as a glucosyl donor in the biosynthesis of an oligosaccharide lipid intermediate by calf brain membranes

When membrane preparations from calf brain are incubated with exogenous [ 14 C]-glucosylphosphoryldolichol, [ 14 C]glucose is enzymatically transferred into an endogenous oligosaccharide lipid. Efficient transfer was achieved by dispersing the lipophilic glucosyl donor in Triton X-100. The transfer of [ 14 C]glucose from exogenous [ 14 C]glucosylphosphoryldolichol into [Glc-[ 14 C]oligosaccharide lipid did not require the addition of a divalent cation, and occurred in the presence of EDTA. The inclusion of Ca 2+ in the reaction mixture resulted in a lower level of [Glc- 14 C]oligosaccharide lipid recovery and the incorporation of label into glycoprotein. If Ca 2+ is added following a 10-min preincubation of membranes with exogenous [ 14 C]glucosylphosphoryldolichol, label is lost from the oligosaccharide lipid fraction and there is a corresponding appearance of label in glycoprotein. The [Glc- 14 C]-oligosaccharide lipid glycosylated via [ 14 C]glucosylphosphoryldolichol in brain membranes is recovered by extraction with CHCl 3 -CH 3 OH-H 2 O (10:10:3). The chromatographic behavior of the labeled oligosaccharide lipid on DEAE-cellulose is similar to that of the oligosacharide lipids in which the oligosaccharide units are bound to dolichol by a pyrophosphate linkage. Consistent with this proposed structure, the [Glc- 14 C]oligosaccharide is released from the carrier lipid by treatment with 0.1 n HCl in 80% tetrahydrofuran at 50°C for 20 min. The free [Glc- 14 C]oligosaccharide unit contains approximately 10 glycose residues based on gel filtration analysis. The presence of two N -acetylated sugars is indicated by the formation of two positively charged products by treatment with strong base and the subsequent electrophoretic neutralization under conditions used for N -acetylation. The labeled product recovered in the delipidated membrane residue following incubation of calf brain membranes with exogenous [ 14 C]glucosylphosphoryldolichol in the presence of Ca 2+ can be solubilized with 1% sodium dodecyl sulfate-0.1% mercaptoethanol (100°C, 2 min). The solubilized product is resolved into two large molecular weight fractions by chromatography on a Bio-Gel A-1.5m column eluted with a buffer containing 0.2% sodium dodecyl sulfate-0.1% mercaptoethanol. Both high molecular weight fractions are converted to low molecular weight products by digestion with Pronase or trypsin. The labeled glycopeptide fraction produced by Pronase digestion is eluted as a single peak on Bio-Gel P-6 and appears to be slightly larger than the glucosylated oligosaccharide released from the carrier lipid by mild acid treatment. Strong acid hydrolysis (3 n HCl, 100°C, 6 h) of the [ 14 C]-glycopeptides released a single radioactive product that cochromatographed with authentic glucose. The electrophoretically neutral [Glc- 14 ]glycopeptide fractions by treatment with mild alkali, indicating that the [Glc- 14 C]oligosaccharide units are probably attached to the polypeptide chains by an N -glycosidic linkage. These results show that in calf brain membranes at least one glucose residue in a glucosylated oligosaccharide lipid is acquired via glucosylphosphoryldolichol, and strongly suggest that in the presence of Ca 2+ the glucosylated oligosaccharide unit can be enzymatically transferred from its carrier lipid into glycoprotein

Analysis of serum blocking factors against leukocyte‐dependent antibody in melanoma patients

AbstractPrevious studies have shown that leukocyte‐dependent antibody activity against melanoma cells in the sera of melanoma patients is often completely blocked by factors in their sera. In the present study, characterization of these factors blocking melanoma LDA was carried out by a number of sequential separation procedures involving gel filtration on Sepharose 6B, affinity chromatography on concanavalin A (Con A) and electrophoresis in polyacrylamide gels in the presence of sodium dodecyl sulphate (PAGE‐SDS). The blocking factors were identified throughout the separation procedure by their blocking activity against melanoma LDA. It was found that blocking activity against melanoma LDA was located in small (<60,000) and large (approx. 300,000) molecular weight fractions obtained by gel filtration. Both of the latter fractions were found to have affinity for concanavalin A and were therefore glucose‐ and/or mannose‐containing glycoproteins. The blocking activity in both fractions was further resolved into a single fraction of 15,000 d by PAGE‐SDS. This small molecular weight fraction appeared to be melanoma antigen as shown by its removal by affinity chromatography on melanoma antibody bound to sepharose and by its blocking activity against melanoma LDA. A similar fraction was isolated by this separation procedure from supernatants and membranes of cultured melanoma cells. These results appear to provide a basis for the development of in vitro assays to monitor tumour growth in melanoma patients and for further characterization of the biological nature of melanoma antigens.

Concentrations and Kinetics of Phosphorus Fractions in Water from Streams Entering Lake Memphremagog

This study examines the possibility that the proportions of different P fractions may vary among rivers, and hence, that the P supplied to lakes may differ in its availability for algae regardless of any similarities in the total P concentration of river waters. Surface water from eight streams and groundwater was collected at roughly monthly intervals from June 1975 to September 1976 and analyzed to determine the concentrations of P fractions and the interrelations between these forms and orthophosphate. Despite differences in total P concentration, (18–64 μg/L) the proportions of P in different fractions were relatively constant seasonally and geographically. Soluble P formed about one third and PO4 < 10% of the total P. These values were not greatly affected by urban drainage but both were increased in small headwater streams during periods of low water. Soluble P was divided into two roughly equal fractions by gel filtration: a large molecular weight fraction (> 5000 mol wt) which eluted at void volume and a small molecular weight fraction (< 400 mol wt) which eluted with 32P-PO4. This latter fraction also included some small organic phosphates. Soluble reactive phosphate consistently overestimated PO4. The exchange of P between PO4 and suspended material was slow in winter and more rapid in summer, although only rivers draining lakes, embayments, or bogs reached the very rapid values reported from lakes. As in lakes, soluble organic P entered into the short-term P dynamics of streams as indicated by the labeling of large molecular weight P during equilibration of river water with radioactive phosphate. This exchange shows that at least a portion of the soluble organic and particulate P is available to the plankton once the river water enters a lake. The uncertainty as to the size of this portion leads to uncertainty in predicting the impact of P loading on lakes. Key words: nutrient budget, P loading, orthophosphate, soluble organic P, drainage basins

Desensitization: II. Passive transfer of the desensitized state by serum from desensitized animals

The present study was undertaken in an effort to elucidate the mechanism(s) responsible for desensitization, making use of both cutaneous and peritoneal manifestations of delayed hypersensitivity as parallel assay systems in the guinea pig model. Particular emphasis was placed on investigating the possibility of passively transferring desensitization with serum factors and attempting to characterize these. Our data support the hypothesis of an inhibitory environment in the anergic animal: The desensitized state was successfully transferred to immune recipients by the systemic administration of desensitized serum as measured by both skin testing and macrophage disappearance reaction (MDR). Transfer of the desensitized state is not due to residual antigen in donor sera and is nonspecific. Partial characterization of the serum inhibitor indicated that it is nondialyzable, heatstable at 56 °C for 30 min, but destroyed by heating at 80 °C for 60 min. Sephadex G-100 chromatography located the inhibitory activity in the size range of 10,000–45,000 daltons. Larger molecular weight fractions were devoid of inhibitory activity, suggesting that antibodies or immune complexes are not responsible for the effect observed and the inhibitory serum component is not associated with macroglobulins. The physicochemical properties of the desensitizing factor, and our previous finding that intravenous injection of lymphokines leads to transient cutaneous anergy, suggest that the desensitizing substances may represent endogenous lymphokines in the general circulation.

Decomposition of aquatic angiosperms. I. Dissolved components

The decomposition of dissolved organic matter (DOM) released from freshwater vascular macrophytes was investigated over a 180-day period under controlled conditions of temperature and oxygen (10 and 25°C; anaerobic and aerobic). Plant species studied were the emergent bulrush Scirpus acutus Bigelow, the floating-leaved water lily Nuphar variegatum Engelm., two submerged plants, Myriophyllum heterophyllum Michx., Najas flexilis (Willd.) Rostk. & Schmidt, and the submersed bulrush, Scirpus subterminalis Torrey. The concentrations of dissolved organic carbon (DOC) released by autolysis and by bacterial metabolism were analyzed in total and fractionated into four molecular weight categories (< 30 000, < 10 000, < 1000, and < 500 Daltons). Ultraviolet absorptive and fluorescence characteristics of each fraction were also analyzed. Decomposition of DOM was most rapid under aerated conditions at either temperature and resulted in declining or consistently low concentrations of DOC in all molecular weight fractions. Fluorescence and UV absorbance of low molecular weight fractions were rapidly reduced to low values, indicative of rapid removal of small compounds with unsaturated bonds or ring structures by bacterial degradation, complexing, or absorption to particulate phases. While the amount of high molecular weight DOC decreased, spectral properties indicated an increasing dominance of complex humic-type compounds. Under aerobic conditions, small and large molecular weight fractions showed consistent losses in total organic carbon at both temperatures. The presence of oxygen was more effective in control of rates of conversion of DOM than was temperature over the range examined in these experiments. A temperature effect was observed, however. At the lower temperature, when anaerobic, DOM was only slowly metabolized, and even low molecular weight fractions accumulated carbon. At the higher temperature, DOM was eventually decomposed even under anaerobic conditions. Decomposition of DOM in aerated cultures proceeded slightly faster at 25 than at 10°C.

The occurence of a neutral protease and its inhibitor in rat peritoneal macrophages.

The lysate of the glycogen-induced macrophages in rat peritoneal exudate was fractionated by centrifugation and extraction into a water extract, 1 M KCl extract and residue fractions. Approximately 50% of the neutral protease activity toward casein in the lysate was recovered in the KCl extract fraction, which was practically devoid of acid protease, cathepsin D. The pH optimum of the neutral protease toward casein and urea-denatured hemoglobin was pH 8.5. The activity was inhibited strongly by DFP or chymostatin and only partially by HgCl2 or PCMB. Addition of a salt to the reaction medium caused enhancement of the activity with an optimum concentration of 0.25 M: KCl, KBr, KI, NaCl, NaBr, NaI, and MgCl2 were all almost equally effective. When the enzyme preparation was filtered through a column of Sephadex G-75 gel in the presence of 1 M KCl, a larger molecular weight fraction at the void volume was obtained in addition to a smaller molecular weight fraction showing a caseinolytic activity insensitive to KCl concentration. The former was found to have a specific inhibitory effect on the latter activity.

Glycopeptide fractions prepared from purified central and peripheral rat myelin

Myelin was purified from rat brain and sciatic nerve after invivo labeling with [ 3H]fucose and [ 14C]glucosamine to provide a radioactive marker for glycoproteins. The glycoproteins in the isolated myelin were digested exhaustively with pronase, and glycopeptides were isolated from the digest by gel filtration on Bio-Gel P-10. The glycopeptides from brain myelin separated into large and small molecular weight fractions, whereas the glycopeptides of sciatic nerve myelin eluted as a single symmetrical peak. The large and small glycopeptide fractions from central myelin and the single glycopeptide fraction from peripheral myelin were analyzed for carbohydrate by colorimetric and gas liquid chromatographic techniques. The glycopeptides from brain myelin contained 2.4 μg of neutral sugar and 0.59 μg of sialic acid per mg total myelin protein, whereas sciatic nerve myelin glycopeptides contained 10 μg of neutral sugar and 3.8 μg of sialic acid per mg total protein. Similarly, the gas-liquid chromatographic analyses showed that the glycopeptides from peripheral myelin contained 4- to 7-fold more of each individual per mg total myelin protein than those from central myelin. Most of the sialic acid and galactose in the glycopeptides from central myelin were in the large molecular weight fraction, and the small molecular weight glycopeptides contained primarily mannose and N- acetylglucosamine . The considerably higher content of glycoprotein-carbohydrate in peripheral myelin supports the results of gel electrophoretic studies, which indicate that the major protein in peripheral myelin in glycosylated while the glycoproteins in purified central myelin are quantitatevely minor components.

SMALL MOLECULAR WEIGHT HYDROXYPROLINE-CONTAINING COMPOUNDS IN THE DEVELOPING MOUSE LIMB

We have found 3 small molecular weight hydroxyproline (OHPro)-containing compounds that are abundant in the developing mouse limb. The amino acid OHPro is customarily related to the presence of collagen and elastin, molecules in the extracellular matrix that contain OHPro. Cells cannot incorporate free OHPro directly into collagen during synthesis; instead OHPro is formed by the post-translational hydroxylation of polypeptide-bound proline. In fibroblast cultures (J. Cell Sci. 12:217, 1973) most of the labeled OHPro made from proline is a free amino acid or in a small polypeptide.We have cultured developing limbs from day 10 to 14 embryos with C14-proline for 4 hrs. Snail and large molecular weight fractions were obtained by chromatography on Sephadex G-25. The amount of C14-OHPro was determined on an amino acid analyzer column. Over 80% of the C14-OHPro was in the small molecular weight fractions and included trans-4-OHPro, Cis-4-OHPro and trans-3-OHPro. These compounds were also produced in the presence of “,αα-dipyridyl, which inhibits the known hydroxylation enzyme. The presence of Cis-4-OHPro is a surprise as it prevents the formation of a stable collagen helix. This compound has never been isolated from mammalian tissues. Trans-3-OHPro is abundant in type TV collagen, the most common source of which is basement membranes. The role (if any) of these 3 srall molecular weight OH-Pro compounds in development remains to be elucidated. Supported by NIH Grants 1009689 and HL18714.

Amino acid sequence studies on the alpha chain of human fibrinogen. Isolation and characterization of two linked alpha-chained cyanogen bromide fragments from fully cross-linked fibrin.

Fully cross-linked human fibrin was digested with cyanogen bromide and the resulting fragments were characterized and compared with the fragments produced upon cyanogen bromide treatment of fibrinogen alpha chains. The largest molecular-weight fraction isolated by gel filtration on Sephadex G-150 was reduced and alkylated, and upon rechromatography on Sephadex G-150 it eluted at the same place as the original material. This large molecular weight fraction was subjected to amino acid analysis and the amino-terminal sequences of its constituent chains were determined by both dimethylaminonaphthyl sulfonation (Dns) and thioacetylation procedures. The identified sequences corresponded to two cyanogen bromide fragments previously found in alpha chains isolated from fibrinogen, one of which has a molecular weight of about 30 000 and the other 6000. The latter is thought to be the carboxy-terminal penultimate cyanogen bromide fragment of the alpha chain.

Evidence for the existence of a large molecular weight protein in human pituitary tissue having follicle stimulating hormone activity.

A large molecular weight protein fraction was isolated during purification of follicle stimulating hormone (hFSH) from acetone preserved human pituitary glands. This large molecular weight fraction, F-1, was not retarded by Sephadex G-100 as was hFSH, nor did it penetrate 7.5% acrylamide gel upon electrophoresis in sodium dodecyl sulfate as did hFSH. There was no evidence of dissociation of F-1 into smaller molecular weight fractions upon its refiltration through Sephadex G-100 or upon electrophoresis, suggesting F-1 was not an aggregate of smaller size proteins. Fraction F-1 stimulated ovarian growth in rats, inhibited binding of 125I-hFSH to rat testes membranes and cross-reacted with antiserum to hFSH, hFSH-alpha subunit and hFSH-beta subunit as determined by radioimmunoassay. Based on gel filtration experiments, it seemed unlikely that immunologic activity against subunit antisera could be attributed to contamination of F-1 by free FSH subunits. The membrane binding activity of F-1 decreased after incubation with 8M urea, but at a rate less than 1/2 that seen with intact hFSH similarly treated, indicating the two activities were not identical. These results suggest that human pituitary tissue contains a large molecular weight protein with FSH-like biologic and immunologic activity, but which is distinct from native hFSH.

Isolation of a peptidyl-pantetheine-protein from tyrocidine-synthesizing polyenzymes.

The polyenzyme complex responsible for the synthesis of tyrocidine in Bacillus brevis (ATCC 8185) was found to contain 4'-phosphopantetheine, which appeared to be connected with the production of growing peptide chains. Confirmation of this assumption has now been obtained by purifying from bacterial lysates a polyenzyme-dissociation product; this was labeled with [(14)C]pantothenic acid and peptide chains containing tritiated amino acids, and had a molecular weight of 17,000. To obtain these results, organisms were grown udner conditions favorable for incorporation of radioactive pantothenic acid into tyrocidine-synthesizing enzymes. A crude lysate of the [(14)C]pantothenic acid-labeled organisms was preincubated with the tritiated amino acids to form enzyme-bound growing peptide chains. The doubly labeled fragments were purified from the polyenzyme-dissociation products produced by prolonged lysis. In a second set of experiments, the three enzymes responsible for tyrocidine synthesis, including the two polyenzymes containing pantetheine, were purified and incubated with radioactive amino acids and ATP to form polyenzyme-bound peptide chains. Thereupon, a Triton X-100 extract of the 20,000 x g fraction of crude homogenate was added to dissociate the purified polyenzymes. The dissociation products were purified and yielded, on dodecyl sulfate gel electrophoresis, peptidyl-marked products ranging in molecular weight from 90,000 to 17,000, the latter being most abundant. Electrophoresis of analogous preparations after preincubation with higher concentrations of dodecyl sulfate and dithiothreitol at 100 degrees yielded a single product of 17,000 molecular weight, indicating that the larger molecular weight fractions were aggregates thereof.

Study of the mechanism of styrene-rubber graft copolymerization

Three stages were found when styrene was graft-copolymerized with rubber, i.e. up to 40–55% polymerization, in which there is a continuous increase in the quantity of graft copolymer, from 40–55 to 94–98%, in which there is hardly any grafting, and the final stage in which there is a 1·7–2·3 fold increase of the amount of graft copolymer. The suggested mechanism for polystyrene (PS) grafting on to rubber in the third stage is a reaction of the large molecular weight fractions and of the growing PS radicals with the double bonds of the rubber; but there is another partial mechanism of trapping the occluded PS by the rubber phase. The intense gel formation during stage 3 is explained by crosslinking of the macromolecular chains of rubber by means of the growing PS radicals. The cast-moulding properties of impact resistant PS were found to depend on its micro structure and the crosslinking density of the network present in the gel.

The partial purification and properties of uridine kinase from Ehrlich ascites tumor cells.

In the partial purification of uridine kinase (ATP:uridine 5′-phosphotransferase, EC 2.7.1.48) from Ehrlich ascites tumor cells, two active fractions were obtained by chromatography on Sepharose 6B. Their molecular weights, as determined by a gel filtration and sucrose density centrifugation, were approximately 120 000 and 30 000. The larger molecular weight species was less stable on incubation at 60° and slightly less sensitive to CTP inhibition than the lower molecular weight fraction. Both fractions were stabilized against heat inactivation by ATP and CTP.The two fractions displayed similar apparent Km values for uridine and ATP, similar specificities for substrates and inhibitors, and similar divalent cation requirements.In the partial purification of uridine kinase from mouse intestine, only the larger molecular weight fraction was obtained by chromatography on Sepharose 6B.In addition, some preliminary evidence for a monomer–polymer relationship between the two molecular weight species is presented.

Urine polyelectrolytes: Binding of phosphate, calcium and magnesium

The chemical and physical properties of urine polyelectrolytes (UPE) from lambs were studied. The large molecular weight fraction of UPE was similar to that of serum proteins but there were some differences that could have been caused by aggregation or dissociation. The small molecular weight fraction contained a large amount of glycine and hydroxyproline consistent with collagen fragments. Amino acid analysis showed that the UPE contain more acidic than basic amino acids, thus are negatively charged. Ultrafiltration studies indicated that inorganic phosphate is bound to the UPE. Because of the negative nature of the UPE the inorganic phosphate is probably bound to cations which are associated with the UPE. This type of binding could result in the formation of the UPE-calcium/magnesium-phosphate complex. Therefore, we propose that the UPE provide the binding sites for magnesium or calcium. The divalent cations would in turn form phosphates which could initiate aggregation to form the matrix.

A substance resembling arginine vasotocin in the anterior pituitary gland of the cockerel.

Fractionation by ultrafiltration of acid extracts of cockerel adenohypophyses revealed 2 components which depleted ovarian ascorbic acid (OAA) in the appropriately pretreated assay rat. Avian LH was retained in the large molecular weight (over 12,000) fraction. In the 32P assay, this fraction evoked a response curve which was parallel to that of the NIH-LH standard. The other fraction, which contained molecules with a molecular weight of less than 12,000, caused depletion of OAA in both intact and hypophysectomized assay rats, but was inactive when tested for its ability to increase 32P uptake by the chick testis. Thus, its OAA depleting activity was due neither to luteinizing hormone (LH) nor to LH-releasing factor. Fractionation of the small molecules on a column of Sephadex G-25 revealed a potent OAA depleting compound with the additional following characteristics: 1) same elution volume as synthetic arginine vasotocin (AVT), 2) potent vasopressor activity, 3) inactivated by thioglycollate. These data ...

Studies on urolithiasis: XII. Association of urine polyelectrolytes

The property of molecular association of urine polyelectrolytes (UPE) consisting of proteins and peptides isolated from the urine of lambs fed on calculus- and non-calculus-provoking rations has been investigated. The UPE showed a variation in degree of association according to the ration and the ionic media in which they were dissolved. There was a greater degree of association in: (1) the UPE in the presence of calcium than magnesium ions, (2) the UPE of the calculus-provoking than the non-calculus-provoking rations, and (3) the UPE of the small molecular weight fraction (less than 5000) than the larger molecular weight fraction (greater than 5000). The UPE seemed to be in more dissociated forms in the presence of NaCl, KCl, and Na 2HPO 4. Dimethyl sulfoxide, which is effective in reducing the incidence of urolithiasis, appeared to be able either to prevent the further association of UPE molecules or to keep the associated molecules in solution. The results of this study showed that the highly associated urine polyelectrolytes, proteins as well as peptides, had apparently contributed to the cause of urinary calculus formation by serving as the calculus matrix.

Interfacial polycondensation. XIII. Viscosity–molecular weight relationship and some molecular characteristics of 6‐10 polyamide

AbstractNumber‐average molecular weights were estimated by determination of endgroups on 6‐10 polyamide samples prepared by stirred and unstirred interfacial polycondensation procedures under varying conditions. Polymers made by melt and interfacial polycondensation methods obeyed the same dilute solution viscosity relationships. However, polymers from interfacial polycondensation reactions deviated in molecular weight distribution from that found for polymers prepared by the melt method. The deviation, which presents the appearance of broader than random distribution, is believed to result to a considerable degree from the presence of an unusually large low molecular weight fraction rather than a continuous distortion of the distribution curve. The interfacially prepared polyamides having the highest viscosity numbers, obtained by adjusting the concentration ratios of the two reactants, showed the least deviation from random distributions. Evidence was found for branching and even network formation in 6‐10 polyamide prepared by interfacial polycondensation as the concentration of the diacid chloride phase was increased. Branching probably occurred through acylation of amide links along the polymer chain to yield imide groups. These groups were cleaved to amide groups in the molten polymer or upon solution in sulfuric acid. Melt‐prepared, unfractionated 6‐10 polyamide followed the relationship [η] = 1.35 × 10−4 M̄n0.96, and a κ′ factor of 0.43 was found in the equation relating solution viscosity to concentration, ηnp/c = [η] + κ′[η]2c, for dilute solution determinations in m‐cresol at 25°C.

The separation by starch electrophoresis of two antibodies in sheep red cells differing in hemolytic efficiency.

A previous report1 described the separation by differential centrifugation of two antibodies in rabbit antiserums to the Forssman and isophile antigens of sheep red cells which differed in hemolytic efficiency. With antiserums to both antigens, it was found that the ratio of hemolysin to combining units (i.e., hemolytic efficiency) increased progressively from top to bottom fractions during centrifugation. The bottom fraction, containing an enriched concentration of large molecular weight globulins, was found to be 10 times as hemolytically efficient as the top fraction, which consisted mainly of smaller molecular weight proteins. While it might be reasonable to assume that the hemolytically efficient antibody associated with the large molecular weight fraction had some combining capacity, the results of this study did not permit a demonstration of hemolytic activity in the less efficient and presumably