抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

The effect of processing variables on the morphology of electrospun nanofibers and textiles

Occurrence, metabolism, metabolic role, and industrial uses of bacterial polyhydroxyalkanoates.

Synthesis, structure and properties of polyhydroxyalkanoates: biological polyesters

This paper presents a number of interesting results on the physical properties of poly-3-hydroxybutyrate (PHB). Data are presented on crystallization kinetics, morphology of melt- and solution-crystallized PHB, the variation of lamellar thickness with crystallization temperature, and the assessment of some thermodynamic quantities. These properties include surface free energies, heat of fusion and melting, and glass transition temperatures. It is shown that the special properties of PHB such as the large spherulite size, which is probably due to its exceptional purity, make it an ideal material for model studies of polymer crystallization and morphology. For example, we show that the variation of growth rate with crystallization temperature is consistent with the very latest theories; and that the single crystal morphology has important implications for the understanding of crystal growth in other polymer systems.

Crystallization and morphology of a bacterial thermoplastic: poly-3-hydroxybutyrate

Polyhydroxybutyrate (PHB) is a bacterially produced thermoplastic. Melt-cast PHB sheets are usually quite brittle. We show that this brittleness is due to cracks within the spherulites. These cracks, which may be either radial or circumferential within the spherulites, depending on the crystallization temperature, form under conditions of no externally applied stress. When the material is strained the cracks grow and join together, leading to brittle failure. It is possible to produce ductile PHB sheets in two ways: first, the cracks may be “healed” by a cold rolling process; second, special crystallization conditions can be used to produce ductile sheets consisting entirely of crack-free spherulites. The relevance of this work to the ductility of crystalline thermoplastic in general is discussed.

The relationship between microstructure and mode of fracture in polyhydroxybutyrate

This article aims to link the mainstream subject of chain-folded polymer crystallization with the rather speciality field of extended-chain crystallization, the latter typified by the crystallization of polyethylene (PE) under pressure. Issues of wider generality are also raised for crystal growth, and beyond for phase transformations. The underlying new experimental material comprises the prominent role of metastable phases, specifically the mobile hexagonal phase in polyethylene which can arise in preference to the orthorhombic phase in the phase regime where the latter is the stable regime, and the recognition of “thickening growth” as a primary growth process, as opposed to the traditionally considered secondary process of thickening. The scheme relies on considerations of crystal size as a thermodynamic variable, namely on melting-point depression, which is, in general, different for different polymorphs. It is shown that under specifiable conditions phase stabilities can invert with size; that is a phase which is metastable for infinite size can become the stable phase when the crystal is sufficiently small. As applied to crystal growth, it follows that a crystal can appear and grow in a phase that is different from that in its state of ultimate stability, maintaining this in a metastable form when it may or may not transform into the ultimate stable state in the course of growth according to circumstances. For polymers this intermediate initial state is one with high-chain mobility capable of “thickening growth” which in turn ceases (or slows down) upon transformation, when and if such occurs, thus “locking in” a finite lamellar thickness. The complete situation can be represented by a P, T, 1/l (l ≡ crystal thickness) phase-stability diagram which, coupled with kinetic considerations, embodies all recognized modes of crystallization including chain-folded and extended-chain type ones. The task that remains is to assess which applies under given conditions of P and T. A numerical assessment of the most widely explored case of crystallization of PE under atmospheric pressure indicates that there is a strong likelihood (critically dependent on the choice of input parameters) that crystallization may proceed via a metastable, mobile, hexagonal phase, which is transiently stable at the smallest size where the crystal first appears, with potentially profound consequences for the current picture of such crystallization. Crystallization of PE from solution, however, would, by such computations, proceed directly into the final stage of stability, upholding the validity of the existing treatments of chain-folded crystallization. The above treatment, in its wider applicability, provides a previously unsuspected thermodynamic foundation of Ostwald's rule of stages by stating that phase transformation will always start with the phase (polymorph) which is stable down to the smallest size, irrespective of whether this is stable or metastable when fully grown. In the case where the phase transformation is nucleation controlled, a ready connection between the kinetic and thermodynamic considerations presents itself, including previously invoked kinetic explanations of the stage rule. To justify the statement that the crystal size can control the transformation between two polymorphs, a recent result on 1 -4-poly-trans-butadiene is invoked. Furthermore, phase-stability conditions for wedge-shaped geometries are considered, as raised by current experimental material on PE. It is found that inversion of phase stabilities (as compared to the conditions pertaining for parallel-sided systems) can arise, with consequences for our scheme of polymer crystallization and with wider implications for phase transformations in tapering spaces in general. In addition, in two of the Appendices two themes of overall generality (arising from present considerations for polymers) are developed analytically; namely, the competition of nucleation-controlled phase growth of polymorphs as a function of input parameters, and the effect of phase size on the triple point in phase diagrams. The latter case leads, inter alia to the recognition of previously unsuspected singularities, with consequences which are yet to be assessed.

/pdf/an-approach-to-the-formation-and-growth-of-new-phases-with-5bq5d1oatc.pdf

An approach to the formation and growth of new phases with application to polymer crystallization: effect of finite size, metastability, and Ostwald's rule of stages

There are many recent reports in the literature of high-strength, high-stiffness polyethylene fibres produced by a variety of techniques, all of which involve at some stage crystallizing the polymer (invariably a high molecular weight material) from solution. In this review we try to place these reports in their proper context and to show how and why the various techniques have been developed. To do this we present brief historical reviews of two distinct subjects: the drawing of single-crystal mats and the preparation of “shish kebabs”. Both of these have, when used in conjunction with very high molecular weight material, led to very strong and stiff fibres. We then describe the recent gel spinning techniques and arrive at the conclusion that there are essentially just two distinct processes involved: the solid state deformation of single crystals, and the crystallization of pre-extended chains to form shish kebabs. Either or both of these processes can occur in gel spinning. In addition to the scientific subject some technical aspects, including material from the patent literature, are also covered.

High-strength polyethylene fibres from solution and gel spinning

The science of domestic and restaurant cooking has recently moved from the playground of a few interested amateurs into the realm of serious scientific endeavor. A number of restaurants around the world have started to adopt a more scientific approach in their kitchens,1–3 and perhaps partly as a result, several of these have become acclaimed as being among the best in the world.4,5

Today, many food writers and chefs, as well as most gourmets, agree that chemistry lies at the heart of the very finest food available in some of the world’s finest restaurants. At least in the world of gourmet food, chemistry has managed to replace its often tarnished image with a growing respect as the application of basic chemistry in the kitchen has provided the starting point for a whole new cuisine. The application of chemistry and other sciences to restaurant and domestic cooking is thus making a positive impact in a very public arena which inevitably gives credence to the subject as a whole.

As yet, however, this activity has been largely in the form of small collaborations between scientists and chefs. To date, little “new science” has emerged, but many novel applications of existing science have been made, assisting chefs to produce new dishes and extend the range of techniques available in their kitchens. Little of this work has appeared in the scientific literature,2,3,6–9 but the work has received an enormous amount of media attention. A quick Google search will reveal thousands of news articles over the past few years; a very few recent examples can be found in China,(10) the United States,11,12 and Australia.(13)

In this review we bring together the many strands of chemistry that have been and are increasingly being used in the kitchen to provide a sound basis for further developments in the area. We also attempt throughout to show using relevant illustrative examples how knowledge and understanding of chemistry can be applied to good effect in the domestic and restaurant kitchen.

Our basic premise is that the application of chemical and physical techniques in some restaurant kitchens to produce novel textures and flavor combinations has not only revolutionized the restaurant experience but also led to new enjoyment and appreciation of food. Examples include El Bulli (in Spain) and the Fat Duck (in the United Kingdom), two restaurants that since adopting a scientific approach to cooking have become widely regarded as among the finest in the world. All this begs the fundamental question: why should these novel textures and flavors provide so much real pleasure for the diners?

Such questions are at the heart of the new science of Molecular Gastronomy. The term Molecular Gastronomy has gained a lot of publicity over the past few years, largely because some chefs have started to label their cooking style as Molecular Gastronomy (MG) and claimed to be bringing the use of scientific principles into the kitchen. However, we should note that three of the first chefs whose food was “labeled” as MG have recently written a new manifesto protesting against this label.(14) They rightly contend that what is important is the finest food prepared using the best available ingredients and using the most appropriate methods (which naturally includes the use of “new” ingredients, for example, gelling agents such as gellan or carageenan, and processes, such as vacuum distillation, etc.).

We take a broad view of Molecular Gastronomy and argue it should be considered as the scientific study of why some food tastes terrible, some is mediocre, some good, and occasionally some absolutely delicious. We want to understand what it is that makes one dish delicious and another not, whether it be the choice of ingredients and how they were grown, the manner in which the food was cooked and presented, or the environment in which it was served. All will play their own roles, and there are valid scientific enquiries to be made to elucidate the extent to which they each affect the final result, but chemistry lies at the heart of all these diverse disciplines.

The judgment of the quality of a dish is a highly personal matter as is the extent to which a particular meal is enjoyed or not. Nevertheless, we hypothesize that there are a number of conditions that must be met before food becomes truly enjoyable. These include many aspects of the flavor. Clearly, the food should have flavor; but what conditions are truly important? Does it matter, for example, how much flavor a dish has; is the concentration of the flavor molecules important? How important is the order in which the flavor molecules are released? How does the texture affect the flavor? The long-term aims of the science of MG are not only to provide chefs with tools to assist them in producing the finest dishes but also to elucidate the minimum set of conditions that are required for a dish to be described by a representative group of individuals as enjoyable or delicious, to find ways in which these conditions can be met (through the production of raw materials, in the cooking process, and in the way in which the food is presented), and hence to be able to predict reasonably well whether a particular dish or meal would be delicious. It may even become possible to give some quantitative measure of just how delicious a particular dish will be to a particular individual.

Clearly, this is an immense task involving many different aspects of the chemical sciences: from the way in which food is produced through the harvesting, packaging, and transport to market via the processing and cooking to the presentation on the plate and how the body and brain react to the various stimuli presented.

MG is distinct from traditional Food Science as it is concerned principally with the science behind any conceivable food preparation technique that may be used in a restaurant environment or even in domestic cooking from readily available ingredients to produce the best possible result. Conversely, Food Science is concerned, in large measure, with food production on an industrial scale and nutrition and food safety.

A further distinction is that although Molecular Gastronomy includes the science behind gastronomic food, to understand gastronomy it is sometimes also necessary to appreciate its wider background. Thus, investigations of food history and culture may be subjects for investigation within the overall umbrella of Molecular Gastronomy.

Further, gastronomy is characterized by the fact that strong, even passionate feelings can be involved. Leading chefs express their own emotions and visions through the dishes they produce. Some chefs stick closely to tradition, while others can be highly innovative and even provocative. In this sense gastronomy can be considered as an art form similar to painting and music.

In this review we begin with a short description of our senses of taste and aroma and how we use these and other senses to provide the sensation of flavor. We will show that flavor is not simply the sum of the individual stimuli from the receptors in the tongue and nose but far more complex. In fact, the best we can say is that flavor is constructed in the mind using cues taken from all the senses including, but not limited to, the chemical senses of taste and smell. It is necessary to bear this background in mind throughout the whole review so we do not forget that even if we fully understand the complete chemical composition, physical state, and morphological complexity of a dish, this alone will not tell us whether it will provide an enjoyable eating experience.

In subsequent sections we will take a walk through the preparation of a meal, starting with the raw ingredients to see how the chemical make up of even the apparently simplest ingredients such as carrots or tomatoes is greatly affected by all the different agricultural processes they may be subjected to before arriving in the kitchen.

Once we have ingredients in the kitchen and start to cut, mix, and cook them, a vast range of chemical reactions come into play, destroying some and creating new flavor compounds. We devote a considerable portion of the review to the summary of some of these reactions. However, we must note that complete textbooks have failed to capture the complexity of many of these, so all we can do here is to provide a general overview of some important aspects that commonly affect flavor in domestic and restaurant kitchens.

In nearly all cooking, the texture of the food is as important as its flavor: the flavor of roast chicken is pretty constant, but the texture varies from the wonderfully tender meat that melts in the mouth to the awful rubber chicken of so many conference dinners. Understanding and controlling texture not only of meats but also of sauces, souffles, breads, cakes, and pastries, etc., will take us on a tour through a range of chemical and physical disciplines as we look, for example, at the spinning of glassy sugars to produce candy-floss.

Finally, after a discussion of those factors in our food that seem to contribute to making it delicious, we enter the world of brain chemistry, and much of that is speculative. We will end up with a list of areas of potential new research offering all chemists the opportunity to join us in the exciting new adventures of Molecular Gastronomy and the possibility of collaborating with chefs to create new and better food in their own local neighborhoods. Who ever said there is no such thing as a free lunch?

https://kitchen-theory.com/wp-content/uploads/2011/10/Molecular-Gatronomy-A-New-Emerging-Scientific-Discipline.pdf

Peter J. Barham

Papers

Crystallization and morphology of a bacterial thermoplastic: poly-3-hydroxybutyrate

The relationship between microstructure and mode of fracture in polyhydroxybutyrate

An approach to the formation and growth of new phases with application to polymer crystallization: effect of finite size, metastability, and Ostwald's rule of stages

High-strength polyethylene fibres from solution and gel spinning

Molecular Gastronomy: A New Emerging Scientific Discipline