Determination of free,esterified, and total serum cholesterol using a sensitive color reaction

A method is described for the enzymatic determination of free and total cholesterol sequentially in either whole serum or the HDL fraction. Measurement of low levels of free cholesterol is facilitated by the substitution of sodium 2-hydroxy-3,5-dichlorobenzene-sulfonate for phenol in the peroxidase-catalyzed indicator reaction. Both free and total cholesterol may be measured in the same tube or separately. These alternatives may appeal to investigators who for various reasons may prefer to perform these determinations either sequentially or separately. The sequential approach is a means of conserving the relatively expensive enzymatic reagents.     

Spectrophotometric study of thiouracil interference in a serum cholesterol determination

A spectrophotometric study of the effect of thiouracil on the determination of cholesterol by FeCl₃ reaction has been described. The depression of the reaction by thiouracil was confirmed and its removal by exchange with the iodate of AgIO₃ studied. It was found that thiouracil appeared to be removed by the exchange, but the iodate that replaced both it, as well as the chloride which is always present, interfered maximally in a FeCl₃-acetic acid protein precipitating system and to a lesser extent in an alcohol-acetone extraction system. One can infer from the results obtained that it would have been more reasonable to use an uncontaminated portion of serum for the determination of cholesterol rather than to carry out an in vitro removal of an in vitro addition of what may have been an unnecessary stabilizing agent.     

Crosslinking of a Single Poly(ionic liquid) by Water into Porous Supramolecular Membranes

Reversible regulation of membrane microstructures via non‐covalent interactions is of considerable interest yet remains a challenge. Herein, we discover a general one‐step approach to fabricate supramolecular porous polyelectrolyte membranes (SPPMs) from a single poly(ionic liquid) (PIL). The experimental results and theoretical simulation suggested that SPPMs were formed by a hydrogen‐bond‐induced phase separation of a PIL between its polar and apolar domains, which were linked together by water molecules. This unique feature was capable of modulating microscopic porous architectures and thus the global mechanical property of SPPMs by a rational design of the molecular structure of PILs. Such SPPMs could switch porosity upon thermal stimuli, as exemplified by dynamically adaptive transparency to thermal fluctuation. This finding provides fascinating opportunities for creating multifunctional SPPMs.     

The problem of irreversibility in Newtonian dynamics

A new type of dissipation function which does not satisfy the Lipschitz condition at equilibrium states is proposed. It is shown that Newtonian dynamics supplemented by this dissipation function becomes irreversible, i.e., it is not invariant with respect to time inversion. Some effects associated with the approaching of equilibria in infinite time are eliminated. New meanings of chaos and turbulence are discussed.     

Spectrophotometric study of drug interferences in an aqueous 17-ketosteroid reaction

A spectrophotometric study of two reported drug interferences in an aqueous Zimmermann reaction for 17-ketosteroids has been described. One drug, Tegretol, did not interfere spectrally with the 17-ketosteroid determination because its Zimmermann reaction spectrum was displaced far enough toward the ultraviolet so there was no significant superimposition of its spectrum with that of 17-ketosteroids. The other drug, Cephalothin, proved to be no problem analytically, because, even though it was Zimmermann-reactive, it was unextractable from acid hydrolyzed urines and therefore could not interfere in the color-forming step.     

A simple prototype procedure for cerebrospinal fluid cholesterol determinations

A preliminary procedure for CSF cholesterol is described which can be considered as a prototype method for the special case in which a biological sample is so dilute with respect to all of its constituents that it can be used as the sole diluent for the reactants used to measure the desired constituent in the specimen. Since it would be comparatively simple to generate a fluorophore in place of the chromophore and thereby increase the sensitivity of the procedure, one could easily alter the limits of the determination and/or the size of the sample needed. This is contemplated as a technique which should result from the prototype procedure described. Avenues for the determination of other constituents such as triglycerides or biuret reactive compounds may possibly be accomplished by using a similar determinative approach. Again, in the specific case of cholesterol one may have to resort to detection devices other than colorimetric in order to achieve strong signals for measurement. Fluorescence appears to be a best first approach to attempt in these circumstances for a final procedure based on the suggested prototype.     

Investigation of the individual stages of 2-alkylbutadiene polymerization with bis-(π-crotylnickel iodide)—II: Propagation reactions

A kinetic study has been made of the polymerizations of isoprene, 2-ethyl- and 2-isopropylbutadienes initiated by bis-(π-crotylnickel iodide). The calculated rate constants of the poly-2-alkylbutadiene chain propagation were correlated with those of anti-syn isomerization of the π-allylic active sites; the previously advanced hypothesis on the decisive role of the end growing unit configuration in determining the microstructure of macromolecules was confirmed.