FREEZING POINTS OF ANTI-COAGULANT SALT SOLUTIONS

By a method involving equilibration of ice and solution, and analysis of the solution, freezing point depressions of solutions of sodium citrate, oxalate, and fluoride have been determined over the range Δ = 0.45 to 0.65°C. Determinations with sodium chloride solutions have confirmed the accuracy of the method. In each case the freezing point depression is given, within 0.002°C., as a linear function of the concentration. By the use of these linear equations it is possible to prepare a solution of any of these four salts isotonic with a given biological fluid of known freezing point, provided the latter falls within the range studied.     

THE ISOELECTRIC POINTS OF THE PROTEINS IN CERTAIN VEGETABLE JUICES

The state in which a protein substance exists depends upon the nature of its combination with acids or bases and is changed by change in the protein compound. The nature of the compound of a protein that exists at any hydrogen ion concentration can be ascertained if the isoelectric point of the protein is known. Accordingly information regarding the isoelectric points of vegetable proteins is of importance for operations in which it may be desirable to change the state of protein substances, as in the dehydration of vegetables. The Protein in Potato Juice.—The hydrogen ion concentration of the filtered juice of the potato is in the neighborhood of 10^–7 N. Such juice contains the globulin tuberin to the extent of from 1 to 2 per cent. The character of the compound of tuberin that exists in nature was suggested by its anodic migration in an electric field. The addition of acid to potato juice dissociated this compound and liberated tuberin at its isoelectric point. The isoelectric point of tuberin coincided with a slightly lower hydrogen ion concentration than 10^–4 N. At that reaction it existed most nearly uncombined. The flow of current during cataphoresis was greatest in the neighborhood of the isoelectric point. This evidence supplements that of the direction of the migration of tuberin, since it also suggests the existence of the greatest number of uncombined ions near this point. At acidities greater than the isoelectric point tuberin combined with acid. The compound that was formed contained nearly three times as much acid as was needed to dissociate the tuberin compound that existed in nature. At such acidities tuberin migrated to the cathode. Though never completely precipitated tuberin was least soluble in the juice of the potato in the neighborhood of its isoelectric point. Both the compounds of tuberin with acids and with bases were more soluble in the juice than was uncombined tuberin. The nature of the slight precipitate that separated when potato juice was made slightly alkaline was not determined. The Protein in Carrot Juice.—The isoelectric point of the protein in carrot juice coincided with that of tuberin. Remarkably similar also were the properties of carrot juice and the juice of the potato. Existing in nature at nearly the same reaction they combined with acids and bases to nearly the same extent and showed minima in solubility at the same hydrogen ion concentrations. The greatest difference in behavior concerned the alkaline precipitate which, in the carrot, was nearly as great as the acid precipitate. The Protein in Tomato Juice.—The protein of the tomato existed in a precipitated form near its isoelectric point. Accordingly it was not present to any extent in filtered tomato juice. If, however, the considerable acidity at which the tomato exists was neutralized the protein dissolved and was filterable. It then migrated to the anode in an electric field. The addition of sufficient acid to make the hydrogen ion concentration slightly greater than 10^–5 N again precipitated the protein at its isoelectric point. At greater acidities migration was cathodic.     

THE MECHANISM OF CHANGE IN RESISTANCE OF ERYTHROCYTES TO HYPOTONIC SALT SOLUTIONS

Ashby''s work on the effects of KCl and NaCl on the resistance to hypotonic hemolysis of K^•-rich and K^•-poor erythrocytes has been repeated with great attention to purity of materials and refinement of technique. The results fail to agree with those of Ashby. 1. KCl produces greater loss in resistance to hypotonic hemolysis than does NaCl, irrespective of the species of the animal from which the cells are taken. 2. While cases of an increase in resistance have been encountered in my experiments, they are either very slight, or else the particular determination is subject to very great uncertainty. The great increases in resistance found by Ashby are not even approached in any of the present series of experiments. 3. Ashby''s generalization that KCl and NaCl have opposite effects on red blood cells, and that the sense of these effects depends on whether the cell is K^•-rich or K^•-poor is not substantiated.     

ISOELECTRIC POINTS FOR THE MYCELIUM OF FUNGI

1. Mycelium of Rhizopus nigricans when stained with certain acid and basic dyes and washed with buffer mixtures of 0.1 M phosphoric acid and sodium hydroxide responded much like an amphoteric colloid with an isoelectric point near pH 5.0. 2. When grown on potato dextrose agar the reaction of which was varied with phosphoric acid the extent of colony growth of Rhizopus nigricans plotted against the initial Sörensen value of the agar produced a double maximum curve with the minimum between the two maxima at initial pH 5.2. 3. When grown in potato dextrose broth the reaction of which was varied with phosphoric acid the dry matter produced by Rhizopus nigricans plotted against the Sörensen value of the broth produced a double maximum curve with the minimum between the two maxima at initial pH 5.2 or average pH 4.9. 4. Mycelium of Rhizopus nigricans placed in buffer mixtures of 0.01 M phosphoric acid and sodium hydroxide of pH 4.1 to 6.3, changed the reaction in most cases toward greater alkalinity. 5. Mycelium of Fusarium lycopersici stained with certain acid and basic dyes and washed with buffer mixtures of 0.1 M phosphoric acid and sodium hydroxide responded much like an amphoteric colloid with an isoelectric point near pH 5.5.     

THE COMPOSITION OF THE CELL SAP OF THE PLANT IN RELATION TO THE ABSORPTION OF IONS

1. Chemical examination of the cell sap of Nitella showed that the concentrations of all the principal inorganic elements, K, SO₄, Ca, Mg, PO₄, Cl, and Na, were very much higher than in the water in which the plants were growing. 2. Conductivity measurements and other considerations lead to the conclusion that all or nearly all of the inorganic elements present in the cell sap exist in ionic state. 3. The insoluble or combined elements found in the cell wall or protoplasm included Ca, Mg, S, Si, Fe, and Al. No potassium was present in insoluble form. Calcium was predominant. 4. The hydrogen ion concentration of healthy cells was found to be approximately constant, at pH 5.2. This value was not changed even when the outside solution varied from pH 5.0 to 9.0. 5. The penetration of NO₃ ion into the cell sap from dilute solutions was definitely influenced by the hydrogen ion concentration of the solution. Penetration was much more rapid from a slightly acid solution than from an alkaline one. It is possible that the NO₃ forms a combination with some constituent of the cell wall or of the protoplasm. 6. The exosmosis of chlorine from Nitella cells was found to be a delicate test for injury or altered permeability. 7. Dilute solutions of ammonium salts caused the reaction of the cell sap to increase its pH value. This change was accompanied by injury and exosmosis of chlorine. 8. Apparently the penetration of ions into the cell may take place from a solution of low concentration into a solution of higher concentration. 9. Various comparisons with higher plants are drawn, with reference to buffer systems, solubility of potassium, removal of nitrate from solution, etc.     

植物群落对景观温度特征指示作用的研究

以德国Kraichgau地区为研究样区,根据转化糖方法获得的野外实测温度数据,就植物群落温度平均指示值在景观尺度上对生境温度的指示效果进行了深入探讨。结果表明：1)群落温度平均指示值与测定的效应温度之间具明显线性正相关;2)群落温度平均指示值能够反映不同坡向条件造成的生境温度差异,但效果随计算方法不同而异。3种不同方法的比较结果说明,直接根据样方资料获得的计算结果,对坡向条件造成的生境温度差异反映明显;3)以样带数据为基础的研究结果对温度随坡向和坡位变化的反映均不够明显。样带没有达到足够的宽度以及样带中局部地段上的种类组成受人为影响严重可能是未达到预期对比效果的主要原因。     

THE ISOELECTRIC POINT OF RED BLOOD CELLS AND ITS RELATION TO AGGLUTINATION

1. The movement of normal and sensitized red blood cells in the electric field is a function of the hydrogen ion concentration. The isoelectric point, at which no movement occurs, corresponds with pH 4.6. 2. On the alkaline side of the isoelectric point the charge carried is negative and increases with the alkalinity. On the acid side the charge is positive and increases with the acidity. 3. On the alkaline side at least the charge carried by sensitized cells is smaller and increases less rapidly with the alkalinity than the charge of normal cells. 4. Both normal and sensitized cells combine chemically with inorganic ions, and the isoelectric point is a turning point for this chemical behavior. On the acid side the cells combine with the hydrogen and chlorine ions, and in much larger amount than on the alkaline side; on the alkaline side the cells combine with a cation (Ba), and in larger amount than on the acid side. This behavior corresponds with that found by Loeb for gelatin. 5. The optimum for agglutination of normal cells is at pH 4.75, so that at this point the cells exist most nearly pure, or least combined with anion and cation. 6. The optimum for agglutination of sensitized cells is at pH 5.3. This point is probably connected with the optimum for flocculation of the immune serum body.