I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

Methods in Enzymology.

THE structure of proteins is probably the most Jvumpapant and possibly the most difficult of the maflpr uifeolved problems of chemistry, at least for the immediate future, and coming at a time when preparations are being made in numerous places to storm this citadel, the present volume is very timely since it gives clear reviews of many of the new methods which will be employed. It reflects the present trend of protein research towards exact analysis and what one might call the ‘classical’ organic approach to the problem. The X-ray method has clear possibilities, but they are more limited and at the same time involve greater difficulties than was originally expected. In his excellent survey of this field, I. Fankuchen sums up the position with regard to crystalline proteins as follows. “Single protein crystals can be made to yield exceedingly detailed X-ray diagrams and yet one must admit that to date the results of such single crystal studies have been disappointing; disappointing because very beautiful and complete data have so far only yielded comparatively meagre results”—a conclusion which broadly coincides with the views expressed in the discussion at the Roentgen celebration in London. It appears that although we can expect definite information about the number and arrangement of protein molecules in the unit cell, a complete structure analysis lies in the distant future; perhaps not a surprising situation when one contemplates the empirical formula recently given by Brand and his co-workers for lactoglobulin, one of the few cases in which the analyses approach finality, namely, C1864 H3012 N468 S21 O576, or particularizing the amino-324 acids by easily recognisable abbreviations, as follows: Gly8 Ala29 Val21 Leu50 Ileu27 Pro15 Phe9 CySH4 (CyS)8 Met9 Try4 Arg7 His4 Lys33 Asp36 Glu24 (Glu-NH2)32 Ser20 Thr21 Tyr9 H2O4! It might perhaps not unfairly be said that the chief contribution of the X-ray studies has been to demand and stimulate more accurate analyses. Advances in Protein Chemistry Edited by M. L. Anson John T. Edsall. Vol. 2. Pp. xiii + 443. (New York: Academic Press, Inc., 1945.) 6.50 dollars

Advances in Protein Chemistry

Molecular diffusion is an omnipresent phenomena that is important in a wide variety of contexts in chemical, physical, and biological processes. In the majority of cases, the diffusion process can be adequately described by Fick's law that postulates a linear relationship between the flux of any species and its own concentration gradient. Most commonly, a component diffuses down the concentration gradient. The major objective of this review is to highlight a very wide variety of situations that cause the uphill transport of one constituent in the mixture. Uphill diffusion may occur in multicomponent mixtures in which the diffusion flux of any species is strongly coupled to that of its partner species. Such coupling effects often arise from strong thermodynamic non-idealities. For a quantitative description we need to use chemical potential gradients as driving forces. The transport of ionic species in aqueous solutions is coupled with its partner ions because of the electro-neutrality constraints; such constraints may accelerate or decelerate a specific ion. When uphill diffusion occurs, we observe transient overshoots during equilibration; the equilibration process follows serpentine trajectories in composition space. For mixtures of liquids, alloys, ceramics and glasses the serpentine trajectories could cause entry into meta-stable composition zones; such entry could result in phenomena such as spinodal decomposition, spontaneous emulsification, and the Ouzo effect. For distillation of multicomponent mixtures that form azeotropes, uphill diffusion may allow crossing of distillation boundaries that are normally forbidden. For mixture separations with microporous adsorbents, uphill diffusion can cause supra-equilibrium loadings to be achieved during transient uptake within crystals; this allows the possibility of over-riding adsorption equilibrium for achieving difficult separations.

/pdf/uphill-diffusion-in-multicomponent-mixtures-2zunmoojde.pdf

Uphill diffusion in multicomponent mixtures

Stochastic models of diffusion with excluded-volume effects are used to model many biological and physical systems at a discrete level. The average properties of the population may be described by a continuum model based on partial differential equations. In this paper we consider multiple interacting subpopulations/species and study how the inter-species competition emerges at the population level. Each individual is described as a finite-size hard core interacting particle undergoing Brownian motion. The link between the discrete stochastic equations of motion and the continuum model is considered systematically using the method of matched asymptotic expansions. The system for two species leads to a nonlinear cross-diffusion system for each subpopulation, which captures the enhancement of the effective diffusion rate due to excluded-volume interactions between particles of the same species, and the diminishment due to particles of the other species. This model can explain two alternative notions of the diffusion coefficient that are often confounded, namely collective diffusion and self-diffusion. Simulations of the discrete system show good agreement with the analytic results.

Diffusion of multiple species with excluded-volume effects

The diffusion coefficients, D ij , for the ternary system water + chloroform + acetic acid are reported at five compositions. This system presents a large solubility gap due to the almost complete insolubility between water and chloroform. The analyzed compositions have a fixed mole ratio of water and chloroform and a decreasing amount of acetic acid when approaching the binodal curve. The difficulty of interpreting the D ij is stressed, and the use of different choices of which component is the solvent and a different reference frame for the diffusive transport is suggested to extract all the possible information from the diffusion coefficients.

Diffusion Coefficients for the Ternary System Water + Chloroform + Acetic Acid at 25 °C

A model is considered in which the bonds of a honeycomb lattice are covered by rodlike molecules of types AA, BB, and AB. Neighboring molecular ends have three-body and orientation-dependent interactions. The model is shown to be equivalent to a spin-1/2 Ising model on the same lattice with a field, but with only pairwise interactions. Symmetric and asymmetric coexistence surfaces for the separation into an AA-rich and a BB-rich phase are calculated exactly.

An exactly solvable model for a ternary solution with three-body interactions and orientationally dependent bonding.

A theoretical spinodal curve for the system water + chloroform + acetic acid at 25 °C is derived using a lattice model for ternary amphiphilic solutions: rod-like molecules covering the bonds of the honeycomb lattice with three-body interactions between the molecular ends associated to the same lattice site. The molecular model is equivalent to the standard Ising model on the same lattice; its mean-field solution is the most appropriate for reproducing, by local fitting, the experimental data for the binodal composition. The derived spinodal curve is in very good agreement with the spinodal composition determined also in the present work from the measured diffusion coefficients recently reported for the same system.

https://rd.springer.com/content/pdf/10.1007%2Fs10953-009-9384-5.pdf

Spinodal Composition of the System Water + Chloroform + Acetic Acid at 25 °C

A model is presented in which the bonds of a honeycomb lattice are covered by rodlike molecules of types AA and BB, molecular ends near a common site having both three-body interactions and orientation-dependent bonding between two A molecular ends and between an A and a B molecular end. Phase diagrams corresponding to the separation into AA-rich and BB-rich phases are calculated exactly. Depending on the relative strengths of the interactions, one of several qualitatively different types of phase diagrams can result, including diagrams containing phenomena such as a double critical point or two separate asymmetric closed loops. The model is essentially a limiting case of a previously considered ternary solution model, and it is equivalent to a two-component system of interacting A and B molecules on the sites of a kagome lattice.

Phase separation in an exactly solvable model binary solution with three-body interactions and intermolecular bonding.

We consider a lattice model for ternary solutions in which the lattice bonds are covered by molecules of types AA, BB, and AB, and the only interactions are between the molecular ends of a common lattice site. Using its equivalence with the standard Ising model for magnets, we derive the spinodal curve of the three-component model on the honeycomb lattice in the mean-field and Bethe-lattice approximations. The spinodal and the coexistence curves of the ternary solution are drawn at different values of the reduced temperature, the only parameter of the model. The particular case of a binary solution is also illustrated.

Florin D. Buzatu

Papers

Diffusion Coefficients for the Ternary System Water + Chloroform + Acetic Acid at 25 °C

An exactly solvable model for a ternary solution with three-body interactions and orientationally dependent bonding.

Spinodal Composition of the System Water + Chloroform + Acetic Acid at 25 °C

Phase separation in an exactly solvable model binary solution with three-body interactions and intermolecular bonding.

Spinodal Curve of a Model Ternary Solution