bluuebunny/crossref_metadata_2025 huggingface dataset:
Vaccination
Authors: Nossal Gustav JV
Published: September 2006

Vaccination is the generic term for immunization procedures. Immunization is a procedure whereby living or nonliving materials are introduced into the body in order to stimulate the lymphoid system with a view to rendering a person or animal immune to a disease.
Vaccines: Subunit
Authors: Ståhl Stefan , Liljeqvist Sissela
Published: September 2006

Subunit vaccines, both purified native components of pathogens and vaccines developed and produced by recombinant techniques, are now dominating in the strive for an ideal vaccine. Subunit vaccines are highly attractive alternatives to the classical vaccines consisting of live attenuated or killed whole bacteria or viruses.
Vaccines:
DNA
Authors: Ulmer Jeffrey B , Donnelly John J
Published: September 2006

Immunization by injection of plasmids encoding foreign proteins has been used successfully as a research tool and to elicit protective immune responses in animal models.
Vaccines: Presentation
Authors: Ertl Hildegund CJ , Xiang Zhi Quan , Pasquini Susanna , Kowalczyk Dariusz W
Published: September 2006

Different types of vaccine formulations selectively favour induction of the immune responses that correlate with protection to challenge with an infectious agent.
Antigens
Authors: Rao Kanury VS
Published: September 2006

The term ‘antigen’ describes molecular species that are capable of specific recognition by one or more constituents of the acquired immune response. Collectively they encompass the entire range, from the simplest of chemical compounds to the most complex of macromolecules.
Antigens: Carbohydrates
Authors: Ravindranath Mepur H , Morton Donald L
Published: September 2006

Carbohydrate antigens are polymeric chains of diverse monomeric sugar molecules. Carbohydrate antigens can induce antibody production without the help of T lymphocytes and are also recognized by cell‐surface lectins.
Bursa of Fabricius
Authors: Nieminen Pia , Liippo Jussi , Lassila Olli
Published: September 2006

The bursa of Fabricius is known to play a central role in the development of the antibody‐producing B‐lymphocyte lineage in birds. The bursa provides an appropriate microenvironment for gene conversion events leading to antibody diversification.
Complement: Alternative Pathway
Authors: Zipfel Peter F
Published: September 2006

The alternative pathway of complement is a powerful and evolutionarily old defence system of innate immunity that inactivates invading microorganisms and pathogens. For survival in an immunocompetent host microbes, viruses, pathogens or modified tissue cells must provide means to interfere with and control alternative pathway reactions at several levels.
Complement: Classical Pathway
Authors: Arlaud Gérard J , Colomb Maurice G
Published: September 2006

The classical pathway of complement is a major recognition system in innate immunity that is found in mammals and other animal species. It triggers various mechanisms via two multimolecular proteases – C1 and the
MBL/MASP complex
– to eliminate pathogenic microorganisms and other‐s from blood and tissues.
Complement Receptors
Authors: Leslie Robert Graham Quinton
Published: September 2006

Complement receptors are membrane proteins expressed on the surface of immune cells. They interact specifically with complement factors leading to the removal of antigen from the circulation.
Endothelial Cells: Immunological Aspects
Authors: Mantovani Alberto , Garlanda Cecilia
Published: September 2006

Endothelial cells regulate the traffic and functions of leucocytes by expressing in a regulated way adhesion molecules and cytokines. They therefore engage in a complex bidirectional interaction with immunocompetent cells.
Haematopoiesis
Authors: Evans Todd
Published: September 2006

Haematopoiesis is the process of forming blood cells, which occurs during embryogenesis and throughout normal life.
Immunology of Birds and Reptiles
Authors: Jaffredo Thierry , Fellah Julien S , Dunon Dominique
Published: September 2006

Protection against disease requires a complex regulated network of interactions between cells and molecules to mount the immune responses. Birds were a pioneer model to study immunology. They have led notably to the identification of the B and T lineages. Sauropsidae consist of two animal groups, reptiles and birds, in which the immune system has been subjected to a variety of selective pressure. This is reflected by differences in the organization and function of their immune system.
t
RNA
Modification
Authors: Motorin Yuri , Grosjean Henri
Published: September 2006

Naturally occurring transfer RNA (tRNA) always contains numerous chemically altered nucleosides formed by enzymatic modification of the primary RNA transcript during tRNA maturation. These stabilize the tRNA architecture and improve its performance in the different interactions in which tRNA is involved, namely in aminoacylation by cognate aminoacyl‐tRNA synthetases, interactions with initiation and elongation factors as well as in decoding of messenger RNA on the ribosome.
Aminoacyl‐tRNA Synthetases
Authors: Arnez John G , Moras Dino
Published: September 2006

Aminoacyl‐tRNA synthetases catalyse a key reaction in protein biosynthesis. They match the 20 amino acids to the genetic code by specifically attaching them to their adaptors, transfer ribonucleic acid (tRNA) molecules.
Transfer RNA Synthetase Proofreading of Amino Acids
Authors: Jakubowski Hieronim
Published: September 2006

In many cases, the intrinsic binding energies of amino acids to aminoacyl‐tRNA synthetases are inadequate to give the required accuracy of translation. This has necessitated the evolution of a second determinant of specificity, proofreading or editing mechanisms that involve the expenditure of energy to remove errors in amino acid selection.
Ribosome Structure and Shape
Authors: Frank Joachim , Agrawal Rajendra K , Verschoor Adriana
Published: September 2006

The ribosome is a macromolecular machine, composed of RNAs and proteins, that synthesizes proteins by stringing together amino acids according to genetic instructions.
Translational Components in Prokaryotes: Genetics and Regulation
Authors: Wagner Rolf
Published: September 2006

The regulation of the biosynthesis of ribosomes, which constitute the catalytic organelles for the translation reaction, is central for the adaptation of bacteria to different growth conditions. The synthesis of the different ribosomal RNA (rRNA) and ribosomal protein (RP) components is controlled and coordinated by a complex network of regulatory mechanisms to adjust the translational capacity to the required cell demands.
Bacterial Ribosomes: Assembly
Authors: Nierhaus Knud H
Published: September 2006

A ribosome consists of 50–70 different components and is, therefore, one of the most complicated structures known in biology. The large number of components requires a highly coordinated synthesis and assembly.
Protein Synthesis Initiation in Prokaryotes
Authors: Grunberg‐Manago Marianne
Published: September 2006

The term ‘translational initiation’ refers to the sequence of events leading up to the formation of the first peptide bond. It is usually the rate‐limiting step of translation and its efficiency can vary by several orders of magnitude. It is therefore a major determinant of the overall expression level for a gene and is a target for a variety of translational control mechanisms.
Initiation Factors in Eukaryotes
Authors: Merrick William C
Published: September 2006

Initiation factors are those proteins that facilitate the assembly of the initiator tRNA, mRNA and ribosomes into an initiation complex. This assembly correctly matches the AUG start codon of the mRNA with the anticodon of the initiator tRNA in the ribosomal P site and thereby determines the translational reading frame.
Elongation Factors: Bacterial
Authors: Czworkowski John
Published: September 2006

Translational elongation factors are extraribosomal proteins required for the addition of amino acids to the polypeptide being synthesized on the ribosome. Sequence comparisons and high‐resolution structural analyses of these proteins in bacteria have revealed striking homologies among them, with important implications for their evolution and function.
Evolution of the Genetic Code
Authors: Watanabe Kimitsuna , Ueda Takuya
Published: September 2006

From the present situation of genetic code so far elucidated for various species of extant organisms, it is speculated that the genetic code system had started from a single or limited number of amino acids and evolved to the universal genetic code which is being used by most present organisms. During evolution the genetic code is changeable by some factors such as directional mutational pressure on genomes and genome economization. The extreme case is the vertebrate mitochondrial genetic code which is greatly deviated from the universal genetic code.
Protein FoldingIn Vivo
Authors: Teter Sarah , Hartl F Ulrich
Published: September 2006

Proteins are composed of linear chains of amino acids. Upon synthesis in the cell, proteins must acquire a specific three‐dimensional structure, a process known as folding, before they can perform their various functions in the cell.
Prebiotic Chemistry
Authors: Lazcano Antonio
Published: September 2006

Life may be the outcome of a process of prebiotic evolution that involved the self‐organization of abiotically synthesized organic molecules.
Haem Biosynthesis
Authors: Labbe‐Bois Rosine , Beaumont Carole
Published: September 2006

The haem biosynthesis pathway consists of a series of enzymatic reactions providing the cells with haem, the end product, and intermediates used as precursors for the synthesis of other tetrapyrrolic pigments, such as the chlorophylls.
Mutagenesis
Authors: Ennis Don G
Published: September 2006

Mutations have a potential for either positive or negative effects on an organism. To combat the deleterious effects of excessive mutagenesis, elaborate systems of enzymes have evolved to correct errors that arise spontaneously in cells or induced following DNA damage. However, DNA must necessarily change as organisms evolve, thus, some low level of mutagenesis is tolerated perhaps even promoted to assure normal and healthy levels of genetic variation of populations.
Nucleotide Excision Repair in Eukaryotes
Authors: Friedberg Errol C
Published: September 2006

Nucleotide excision repair is the process whereby eukaryotic cells repair damaged DNA by the excision of damaged bases as oligonucleotide fragments. Several genes have been identified as expressing proteins important for the repair mechanism and have therefore been implicated in the related human hereditary diseases.
Ribonucleotide Reduction
Authors: Gleason Florence Kowalczyk
Published: September 2006

Ribonucleotide reductase is an essential enzyme that supplies the precursors for DNA synthesis. Three classes of reductases are known. These differ in primary structure, substrate and cofactor requirements, but all use a protein radical to catalyse reduction.
Human Mismatch Repair: Defects and Predisposition to Cancer
Authors: Karran Peter
Published: September 2006

Mismatch repair edits DNA replication and reduces spontaneous mutation rates. Individuals with inherited mutations in a mismatch repair gene are susceptible to cancer, and the absence of mismatch repair renders their tumours resistant to some anticancer drugs.
Methanogenesis Biochemistry
Authors: Ferry James G
Published: September 2006

Methanogenesis is the biological production of methane mediated by three major pathways: (1) reduction of carbon dioxide, (2) fermentation of acetate, and (3) dismutation of methanol or methylamines. Investigations of the biochemistry of the pathways have revealed novel enzymes with metal and cofactor requirements that have introduced new principles of biochemistry.
DNA
Repair by Reversal of Damage
Authors: Memisoglu Asli , Samson Leona D
Published: September 2006

Some DNA repair mechanisms involve the simple reversal of DNA damage. These processes require a single protein that is able first to recognize DNA damage, and then to catalyse the reversal of damage to the DNA, thus restoring the DNA to its original state.
SOS
Response
Authors: Defais Martine , Devoret Raymond
Published: September 2006

Bacteria have developed an SOS response to mend DNA damage provoked by deleterious agents such as radiations and chemicals. Mutagenesis, one of the SOS functions, has permitted bacteria to adapt to short‐term and long‐term adverse living conditions.
RecBCDHelicase/Nuclease
Authors: Arnold Deana A , Kowalczykowski Stephen C
Published: September 2006

The RecBCD enzyme ofEscherichia coliparticipates in several aspects of DNA recombination and repair. It is essential to the main pathway of genetic homologous recombination, where it contributes to the exchange of genetic material between homologous DNA molecules (i.e. conjugal recombination), and to the recombinational repair of potentially lethal chromosomal double‐stranded breaks.
DNATransposition: Classes and Mechanisms
Authors: Braam Lisa AM , Reznikoff William S
Published: September 2006

Transposons are mobile genetic elements that contribute to the dynamic nature of chromosomes. Mechanistically similar, transposable elements make up a diverse classification including bacterial insertion sequences and composite transposons and eukaryotic excision/insertion transposons and retroelements.
Transposons: Prokaryotic
Authors: Harshey Rasika M
Published: September 2006

Transposons are movable genetic elements found ubiquitously in the genomes of living organisms. They generate a variety of DNA rearrangements that have profound consequences for cell survival and evolution.
Transposons: Eukaryotic
Authors: Becker Heinz‐Albert , Lönnig Wolf‐Ekkehard
Published: September 2006

Eukaryotic transposons are distinct mobile DNA sequences, many of which can autonomously ‘jump’ from their locations and insert into nonhomologous parts of the genome.
Transposases and Integrases
Authors: Craig Nancy L
Published: September 2006

Transposases and integrases are the proteins that mediate transposition reactions, i.e. the recombination reaction in which discrete DNA segments move between nonhomologous sites.
Immunoglobulin Gene Rearrangements
Authors: Lieber Michael
Published: September 2006

V(D)J and class switch recombination are two DNA recombination processes that occur at immunoglobulin genes during the generation of B cells and the attendant rearrangement of immunoglobulin heavy and light chain loci. V(D)J occurs during early B‐ and T‐cell development whilst class switch recombination occurs exclusively in mature B cells.
Yeast Mating Type
Authors: Montelone Beth A
Published: September 2006

Yeast mating type is determined by alleles of a single genetic locus that encodes regulatory proteins governing genes encoding mating pheromones, pheromone receptors and downstream effectors regulating cell type. Some yeast are capable of switching mating type, a process involving gene replacement by information from silenced copies of the mating type locus found elsewhere in the genome.
Enzymes: Irreversible Inhibition
Authors: Tipton Keith F
Published: September 2006

Many drugs that are in clinical use work by irreversibly inhibiting specific enzymes, either in the individual being treated or in an invading organism. Enzyme inhibitors are also of value for understanding the behaviour of individual enzymes and metabolic systems.
Acid–Base Catalysis by Enzymes
Authors: Kirby Anthony John
Published: September 2006

Proton transfer is the commonest reaction that enzymes perform. Most enzyme reactions go by ionic mechanisms, involving the creation or disappearance of charge. Such reactions are typically acid‐ or base‐catalysed, but acid and base concentrations are minimal under physiological conditions near pH 7. Enzymes have evolved subtle but highly effective solutions to this problem.
Thermodynamics in Biochemistry
Authors: Alberty Robert A
Published: September 2006

The thermodynamics of chemical reactions and biochemical reactions (enzyme‐catalysed reactions at specified pH) deals with equilibrium constants
K
of chemical reactions and apparent equilibrium constants
K
′ for biochemical reactions, reduction potentials for chemical half‐reactions and apparent reduction potentials for biochemical half‐reactions.
Phosphoryl Transfer Reactions
Authors: Hengge Alvan C
Published: September 2006

Phosphoryl transfer is the name given to the chemical process of the transfer of the phosphoryl group (PO3) from a phosphate ester or anhydride to a nucleophile. Nucleophilic attack by water on a phosphate monoester gives the hydrolysis product inorganic phosphate. This net dephosphorylation reaction is the process catalysed by phosphatases. The formation of phosphate esters is termed phosphorylation, and is accomplished in biological systems by kinases.
Cholesterol Metabolism Regulation
Authors: Metherall James E , Nash Elizabeth A , Warnick Darren C
Published: September 2006

A complex set of homeostatic mechanisms maintains strict control over the level of free cholesterol within the cell. Disruption of these mechanisms can lead to developmental and/or neurodegenerative disorders as well as increased levels of circulating low‐density lipoprotein and an increased risk of coronary artery disease.
Adenosine Triphosphate
Authors: Cohn Mildred
Published: September 2006

Adenosine triphosphate consists of the purine adenine linked through its N9 tod‐ribose via a β‐N‐glycosidic C(1′) linkage; the α‐phosphoryl group is linked via an ester linkage to the alcoholic O of ribose (C5′) and the β‐ and γ‐phosphoryl groups form anhydride bonds. The chemical energy stored in the anhydride bonds is released upon hydrolysis at the γ‐ or β‐phosphorus.
Proteoglycan
Authors: Schwartz Nancy B
Published: September 2006

Proteoglycans are complex extracellular macromolecules consisting of a multidomain core protein to which are attached one or more glycosaminoglycan chains.
Coenzymes and Cofactors
Authors: Broderick Joan B
Published: September 2006

Coenzymes and cofactors are molecules or ions that are used by enzymes to help catalyse reactions. Coenzymes are typically organic molecules that contain functionalities not found in proteins, while cofactors are catalytically essential molecules or ions that are covalently bound to the enzyme.
Protein Translocation Across Membranes
Authors: Ryan Michael T , Pfanner Nikolaus
Published: September 2006

Genes found in the nucleus encode almost all enzymes. Enzymes, along with proteins involved in their maintenance, must therefore be targeted to their correct destination. Proteins are synthesized with signal sequences that guide them to receptor proteins that in turn transfer them to large transmembrane protein channels of organelles. Following their translocation across membranes, the newly inserted proteins are often folded with the assistance of molecular chaperones.
Nitric Oxide: Synthesis and Action
Authors: Wu Kenneth K
Published: September 2006

Nitric oxide is an important mediator of diverse physiological functions such as vascular relaxation, neurotransmission and host defence. It is synthesized endogenously by the action of nitric oxide synthases and formed from organic nitrates and nitrites. Through its action on guanylyl cyclase it increases cellular levels of cyclic GMP, which accounts for most NO activities. Excessive NO production causes tissue damages through its direct actions on intracellular constituents and its formation of peroxynitrite with superoxide.
Metabolic Turnover
Authors: Nielsen J
Published: September 2006

Metabolic turnover is the sum of all biochemical reactions – the metabolic network – within a living cell that are involved in the conversion of substrates, particularly carbon, nitrogen and energy sources into Gibbs free energy, secreted metabolites and cell mass. Analysis of metabolic turnover involves identification of which reactions are active in a cell, and of quantifying the fluxes carried by the branches of the network and elucidating how these fluxes are controlled. Control of fluxes takes place at many levels, but the usual distinction is between global and local control.
Saccharomyces cerevisiae
: Applications
Authors: Pausch Mark H , Kirsch Donald R , Silverman Sanford J
Published: September 2006

The yeast Saccharomyces cerevisiae has traditionally found useful applications in the production of food and alcoholic beverages. The completed sequence of its genome has revolutionized the use of yeast as a model system for the investigation of eukaryotic cell processes at a whole‐genome level. The production of enzymes and recombinant proteins and the development of drug screening assays are commercial applications of yeast cells.
NAD
+
and
NADP
+
as Prosthetic Groups for Enzymes
Authors: Oppenheimer Norman J
Published: September 2006

NAD(P)
+
serves as a cosubstrate of pyridine nucleotide‐dependent dehydrogenases. When the coenzyme is nondissociable it can function as a prosthetic group promoting dismutation, epimerization, and rearrangement reactions.
Enzymes: Coenzyme
A
dependent
Authors: Shoolingin‐Jordan Peter M , Crump Matthew P
Published: September 2006

A large group of unrelated enzymes involved in primary and secondary metabolism utilize a thiol group to form acyl thiol esters. The enzymes form noncovalent interactions with the coenzyme A moiety and utilize the ketonic properties of the thiol ester to facilitate acyl transfer and nucleophilic activation.
Chaperones, Chaperonin and Heat‐Shock Proteins
Authors: Consalvi Valerio , Chiaraluce Roberta
Published: September 2006

The protein folding of a nascent polypeptide is the decoding of the linear information contained in the primary sequence into the native three‐dimensional conformation. Chaperone proteins and folding catalysts may contribute to successful folding.
Protease Complexes
Authors: Finley Daniel
Published: September 2006

Proteolysis is one of the most widespread mechanisms for biological regulation, providing control over such diverse phenomena as cell cycle progression, programmed cell death, blood clotting, complement activation, antigen presentation, inflammation, nutrient utilization, long‐term memory, cell migration and circadian rhythms.
Biotin
Authors: Waldrop Grover L
Published: September 2006

Biotin is a vitamin that is a cofactor for enzymes involved in carbon dioxide metabolism. Avidin and streptavidin are proteins that bind biotin very tightly.
Cytochrome
c
Oxidase
Authors: Wikström Mårten
Published: September 2006

Cytochrome
c
oxidase is the key enzyme of cell respiration in all eukaryotes and many prokaryotes. The cytochrome
c
oxidases actually comprise a whole family of structurally and functionally related enzymes.
Folates
Authors: Blakley Raymond L
Published: September 2006

Folates are hydrogenated forms of the vitamin folic acid present in biological materials. Enzymes attach one of several additional groups to tetrahydrofolate, each of these groups containing a single carbon atom. In cellular synthesis of the building blocks required for making nucleic acids and proteins, utilization of the one‐carbon groups attached to tetrahydrofolate is essential.
Quinone Cofactors
Authors: Schwartz Benjamin , Klinman Judith P
Published: September 2006

Quinone cofactors are used by several classes of enzymes that catalyse the oxidation of biogenic amines and alcohols to help catalyse these reactions. Previous to 1990 only one cofactor, pyrroloquinoline quinone, had been identified, but from 1990–1996 three new quinone prosthetic groups derived from naturally occurring amino acids have been discovered.
S‐Adenosylmethionine
Authors: Markham George D
Published: September 2006

S‐Adenosylmethionine is one of the few sulfonium ions found in nature. The positively charged sulfonium centre endowsS‐adenosylmethionine with a chemical versatility matched by few other biochemicals, perhaps only adenosine triphosphate (ATP). Thus, not only isS‐adenosylmethionine used in a multitude of metabolic pathways, but the types of chemical reactions in which it partakes are highly varied, ranging from alkylation to free radical formation.S‐Adenosylmethionine and its metabolites play essential roles in the metabolism of all known organisms; it appears to be one of the molecules required for life.
Cobalamin Coenzymes and Vitamin B
12
Authors: Banerjee Ruma
Published: September 2006

Cobalamins are derivatives of vitamin B
12
and serve as cofactors in various enzymatic reactions. Novel chemical reactions involving either radicals or supernucleophilic intermediates are catalysed by B
12
enzymes.
Proteases
Authors: Barrett Alan J
Published: September 2006

Proteases are catalytically active proteins (enzymes) that break down proteins and fragments of proteins by hydrolysis.
Muscle Contraction: Regulation
Authors: Squire John M
Published: September 2006

Muscular contraction is remarkable in that we can instruct our arms or legs to move, and normally they do it. We can directly control or regulate the activity of our skeletal muscles. Muscular movement is produced by the interaction of the proteins myosin and actin. In vertebrate striated muscles, such activity is regulated by the accessory proteins tropomyosin and troponin.
Muscle Contraction Mechanism: Use of Synchrotron X‐ray Diffraction
Authors: Wakabayashi Katsuzo , Ueno Yutaka , Takezawa Yasunori , Sugimoto Yasunobu
Published: September 2006

Muscle contraction occurs when the muscle proteins actin and myosin interact, powered by hydrolysis of ATP. It is a physical process that transduces chemical into mechanical energy, producing directional motion. X‐ray diffraction with synchrotron radiation has demonstrated a structural basis for the molecular mechanism underlying muscle contraction. Conformational changes in actin and myosin are coordinated to perform efficient energy transduction in the actomyosin motor system.
Tubulin and Microtubules
Authors: Amos Linda A
Published: September 2006

The protein tubulin is the principal constituent of microtubules, whose dynamic behaviour allows them to perform a vital role in various forms of cell motility. Found in almost all types of eukaryotic cell, microtubules are an essential component of cell division, provide tracks for the transport of cellular organelles and vesicles and are responsible for the relative positioning of cellular compartments.
ATPases: Ion‐motive
Authors: Guillain Florent , Mintz Elisabeth
Published: September 2006

Ion motive ATPases allow ion(s) to accumulate on one side of a biological membrane at the expense of ATP hydrolysis. In this way active transport across biological membranes is mediated.
Elongation Factor 3 in Fungal Translation
Authors: Chakraburtty Kalpana
Published: September 2006

Elongation factor 3 (EF‐3) is uniquely required by the fungal translational apparatus. Understanding its function may provide new insights into the mechanistic aspect of translation for all systems. The information in turn may lead to the development of potential antifungal drugs.
Carbohydrates
Authors: Sturgeon Robert J
Published: September 2006

The carbohydrates comprise one of the major groups of naturally occurring organic molecules and are amongst the most abundant constituents of plants, animals and microorganisms. In general, carbohydrates are polyhydroxy‐aldehydes or ‐ketones. They may contain, in addition, amino, acetamido and carboxyl functional groups.
Glycosides: Naturally Occurring
Authors: Cheeke Peter R
Published: September 2006

Glycosides are substances produced in plants by metabolic processes. They are usually bitter‐tasting and are important in human and animal nutrition and they have both toxic and beneficial properties. The most important glycosides are saponins, glucosinolates, cyanogenic glycosides, cardiac glycosides, and other glycoalkaloids.
Chitin
Authors: Martínez José P , Gozalbo Daniel
Published: September 2006

Chitin is a naturally occurring fibre‐forming polymer that plays a protective role in many lower animals similar to that of cellulose in plants. Chemically it is a long‐chain unbranched polysaccharide made of
N
‐acetylglucosamine residues; it is the second most abundant organic compound in nature, after cellulose.
Cellulose: Structure and Distribution
Authors: Stone Bruce
Published: September 2006

Cellulose, a (1→4)‐β‐glucan, is the most abundant carbohydrate polymer in the biosphere, where it may account for 50% of the carbon. Cellulose has a structural and protective function in walls of plant cells and surfaces of other organisms. The insolubility and high textile strength of cellulosic materials arises from the regular, extended, ribbon‐like conformation of the individual molecules, their enormous lengths and their ability to aggregate into crystalline microfibrils.
Polysaccharides: Plant Noncellulosic
Authors: Morrison Ian M
Published: September 2006

Plant cell walls are composites that consist of polysaccharides, proteins and, if they are secondary cell walls, lignin as well as a number of minor constituents. The major components are the polysaccharides and, owing to their complexity, they are usually subdivided into cellulose and others, namely the noncellulosic polysaccharides. These noncellulosic polysaccharides encompass pectins (
d
‐galacturonans) and hemicelluloses (
d
‐xylans,
d
‐glucans,
d
‐mannans, etc.) and each has its own specific function and responsibility within a particular type of cell wall.
Pectic Substances
Authors: O'Neill Malcolm A , Darvill Alan G , Albersheim Peter
Published: September 2006

Pectins are plant polysaccharides comprising mainly 1,4‐linked α‐
d
‐galactosyluronic acid. They are found in the primary cell walls of all seed‐bearing plants and in the junction between cells.
Polysaccharides: Energy Storage
Authors: Robyt John F
Published: September 2006

Storage polysaccharides such as glycogen in animals and starch in plants represent a major energy reserve in living organisms.
Lipopolysaccharides
Authors: Helander Ilkka M , Mamat Uwe , Rietschel Ernst Th.
Published: September 2006

Lipopolysaccharides are structural components of the outer membrane of Gram‐negative bacteria. They are important antigens and exhibit versatile biological (endotoxic) activities through stimulation of mammalian cells to produce active mediators.
Glycosaminoglycans: Structure and Biological Functions
Authors: Antonio James D San , Iozzo Renato V
Published: September 2006

Glycosaminoglycans are among the most complex polysaccharide chains that are either covalently linked to protein cores (to form proteoglycans) or free as unsulfated hyaluronan. They exist associated with virtually all cell surfaces and extracellular matrices of higher organisms, where their fine structure facilitates interactions with proteins, which underlie their myriad biological functions.
Cell Surface Glycoconjugates
Authors: Verbert André , Cacan René
Published: September 2006

In eukaryotic cells, the interface between the extracellular space and the intracellular matrix is formed of a lipid bilayer in which structural or functional proteins are anchored. Carbohydrates also form components of the cell surface, as glycoconjugates, i.e. glycolipids or glycoproteins. Although the carbohydrate moieties account for a minor part in mass (5–10%), their location at the external face of the membrane confers upon them unique biological functions as ‘recognition signals’.
Enzymes: General Properties
Authors: Bugg Timothy DH
Published: September 2006

Enzymes are polypeptide macromolecules that catalyse, or speed up, all biochemical reactions.
Fatty Acids: Structures and Properties
Authors: Rustan Arild C , Drevon Christian A
Published: September 2006

Fatty acids play a key role in metabolism: as a metabolic fuel, as a necessary component of all membranes and as a gene regulator. In addition, fatty acids have a number of industrial uses.
Enzyme Specificity and Selectivity
Authors: Hedstrom Lizbeth
Published: September 2006

Specificity distinguishes enzymes from ordinary chemical catalysts. Specificity is evident in both discrimination between substrates and control of reaction outcome. Specificity arises from the three‐dimensional structure of the enzyme active site.
Enzymatic Rate Enhancements
Authors: Quinn Daniel M , Sikorski R Steven
Published: September 2006

Enzymatic rate enhancements arise from the unmatched ability of enzymes to stabilize the transition states of the reactions that they catalyse.
Enzyme Kinetics: Steady State
Authors: Cleland W Wallace
Published: September 2006

The kinetics of enzyme‐catalysed reactions can be analysed in terms of steady state models if the substrate concentrations are more than an order of magnitude higher than the enzyme level. Such analysis yields Michaelis constants, maximum velocities, and useful information on reaction mechanisms.
Xenopus
Embryo: Neural Induction
Authors: Moody Sally A
Published: September 2006

Neural induction is the process by which the embryonic ectoderm is instructed to become the nervous system rather than the epidermis (skin). It is accomplished in two steps via signalling interactions with the adjacent mesoderm; first, dorsal ectoderm acquires an anterior neural fate by the blockade of bone morphogenetic protein (BMP) signalling, and second, the neural ectoderm acquires anterior–posterior polarity via graded concentrations of fibroblast growth factors (FGFs), retinoids and Wnts.
Eye Development: Gene Control
Authors: Hill Robert E , Hammond Katherine L
Published: September 2006

Molecular analysis of developmental control genes is providing novel insights into evolutionary processes. A survey of a range of species examining the Pax6 gene and its expression in the eye suggests a closer evolutionary relationship than expected for eyes as diverse as the planarian eyespot and the complex organ of the mouse. Analysis of other developmental genes, particularly in mouse and Drosophila, raises further questions about evolutionary mechanisms.
Heart Development: Gene Control
Authors: Krieg Paul A
Published: September 2006

The genetic pathways underlying heart development are conserved in widely different organisms. Multiple regulatory factors cooperate to regulate formation of the mature heart.
Vertebrate Embryo: Neural Patterning
Authors: Itasaki Nobue
Published: September 2006

The central nervous system in vertebrate embryos arises from a flat sheet of neural cells. Anteroposterior patterning involves neural induction through the interaction of precursor cells with non‐neural cells, signalling mechanisms after neurulation, and establishment of
Hox
gene expression patterns. Dorsoventral patterning is organized by a balance of Sonic hedgehog (Shh) and bone morphogenetic protein (BMP) signals that emanate from the ventral and dorsal sides of the neural tube, respectively.
Closteroviridae
Authors: Martelli Giovanni P , Candresse Thierry
Published: September 2006

The
Closteroviridae
is a family of plant viruses with very large, positive‐sense, single‐stranded genomes. It comprises at least two genera,
Closterovirus
and
Crinivirus
, members of which are major insect‐transmitted pathogens, causing extensive damage to sugarbeet, citrus, grape and vegetable crops.
Geminiviridae
Authors: Stanley John , Boulton Margaret I , Davies Jeffrey W
Published: September 2006

The
Geminiviridae
are a group of plant viruses with small, circular, single‐stranded DNA genomes encapsidated in particles that have a twinned quasi‐icosahedral (geminate) shape, from which the family derives its name. They are pathogens of cereals, vegetable and fibre crops, and pose a serious threat to agriculture worldwide.
Plant Viruses with Rod‐shaped Virions
Authors: Robinson David J
Published: September 2006

Seven genera of plant viruses have rigid, rod‐shaped particles. These viruses have similarities and differences in their molecular and biological properties, and many are important disease agents.
Potyviridae
Authors: Berger Philip H
Published: September 2006

The Potyviridae are single‐stranded plus‐sense plant‐infecting RNA viruses, transmitted by aphids, whiteflies, fungi, eriophyid mites, and/or via tubers or true seed, depending on the species. Virions are flexous rods of 680–900 nm in length.
Virus and Host Plant Interactions
Authors: Maule Andrew J
Published: September 2006

The establishment of the compatible interaction between viruses and plants, and the consequences of that interaction, lead to the development of disease and virus transmission.
Epidemiology of Plant Virus Diseases
Authors: Robert Yvon
Published: September 2006

The epidemiology of plant virus diseases concerns the cyclical development of virus diseases within plant populations in time and space. It deals with how and why a virus is spread by vectors in an ecosystem and is fundamental to the choice and improvement of control methods in agriculture.
Plant Virus Transmission by Insects
Authors: Raccah Benjamin
Published: September 2006

Insect vectors of plant viruses are found in 9 of the 32 orders of the class Insecta. Insects transmit plant viruses by four major transmission modes and a number of viral proteins have been found to control virus–vector association. Interference with vector landing and/or with the transmission process is used to control virus epidemics.
Virus Diseases of Potatoes
Authors: Salazar LF
Published: September 2006

Around 30 different viruses are known to affect potatoes, contributing to degeneration of the crop. In response, major efforts have been made to control virus diseases by eliminating them from propagation stocks and developing resistant cultivars, procedures whose effectiveness rely on proper identification of viruses and their detection by means of sensitive and accurate virus detection technology.
Comoviridae
: Plant Picorna‐like Viruses
Authors: Le Gall Olivier , Wellink Joan
Published: September 2006

The
Comoviridae
are plant viruses that share many structural and functional features with animal and human viruses of the family
Picornaviridae
.
Virus Diseases of Grapevine
Authors: Martelli Giovanni P
Published: September 2006

Virus diseases of grapevines (Vitisspp.) are many and often have a detrimental effect on the vines and the crop. Prevailing disease agents are viruses transmitted by nematodes (nepoviruses) and mealybugs (closteroviruses, vitiviruses). Control is based on preventive measures such as selection, sanitation, and breeding for resistance.
Invertebrates and Fungi in Plant Virus Diseases
Authors: Eppler Arne , Heinze Cornelia , Adam Günter
Published: September 2006

Plant viruses rely on effective modes of spread from one plant to another in order to survive. The commonest means of dissemination in the field is by plant‐feeding invertebrates such as nematodes, mites and insects, but plant pathogenic soil‐borne fungi with mobile stages can also serve as vectors.
Cyanophages
Authors: Suttle Curtis A
Published: September 2006

Cyanophages are viruses that infect cyanobacteria (blue‐green algae). They are widespread and abundant in aquatic environments and are important mortality agents in aquatic microbial communities. Increasingly they are being recognized as important players in global geochemical cycles.
Microviruses
Authors: Incardona Nino L
Published: September 2006

Microviruses are among the smallest DNA viruses that infect prokaryotes. The microvirus genomes have features in common with plasmids, the extrachromosomal DNA found in prokaryotes.
Vertebrate Central Nervous System
Authors: Ward Roger
Published: September 2006

The central nervous systems of all vertebrate species share a great many features, including the spinal cord and the four major components of the brain.
Neural Crest: Origin, Migration and Differentiation
Authors: Erickson Carol A
Published: September 2006

The neural crest is a population of cells that emigrates from the dorsal neural tube during early embryogenesis and migrates extensively to give rise to a myriad of cell types. Patterns of migration are controlled largely by extracellular cues in the environment. Cell fates are determined both by specification events while the cells are still resident in the neural tube and by extracellular cues the cells perceive as they migrate.
Cerebral Cortex Development
Authors: Götz Magdalena
Published: September 2006

In the developing cerebral cortex, some aspects of neuronal phenotype are specified even before neurogenesis, whereas others remain plastic for some time postnatally. The combination of early specification and later plasticity creates the multitude of cell types in the cerebral cortex.
Visual System Development in Vertebrates
Authors: Johnson Karl G , Shewan Derryck , Holt Christine E
Published: September 2006

The development of a functional visual system from a variety of simple embryonic structures involves a complex series of inductive and interactive events. The molecular and cellular interactions involved in these processes are now beginning to be unravelled.
Drosophila
Neural Development
Authors: Torroja Laura , White Kalpana
Published: September 2006

Recent advances in developmental neurobiology have confirmed that the molecules that make the nervous system have been conserved through evolution. The study of
Drosophila melanogaster
has been decisive for our understanding of this process.
Vertebrate Central Nervous System: Pattern Formation
Authors: Lumsden Andrew
Published: September 2006

Deciphering the genetic instructions used by the embryo to establish the spatial order of its neuronal populations and their interconnections is the key to understanding the wonderfully complex structure of the adult brain.
Neuronal Migration
Authors: Wong Kit , Wu Jane Y , Rao Yi
Published: September 2006

Cell migration is a major event in neural development and its abnormalities cause human diseases. Cell–cell interactions are important for neuronal migration. Secreted proteins can guide the direction of neuronal migration through intracellular signal transduction pathways that regulate cytoskeletal organization.
Specific Neural Connection Formation in the Developing Nervous System
Authors: Lett Robyn LM , O'Connor Timothy P
Published: September 2006

In order to construct a properly functioning nervous system, neurons must form precise and specific connections during embryonic development. To establish these connections axons are guided to their correct targets by specific guidance cues. Guidance cues are arranged in such a manner that axons extend to a series of transient intermediate targets before forming a synapse with their final, specific, target.
Axon Growth
Authors: Tannahill David , Nobes Catherine
Published: September 2006

In order to construct the nervous system, nerve cells become precisely connected to each other and to peripheral tissues during embryogenesis by a process that involves the growth and extension of long processes, known as axons. Located at the tip of the growing axon is a highly specialized structure called the growth cone that senses information in the embryonic environment to direct axon growth towards appropriate targets.
Molecular Biology: The Central Dogma
Authors: Pukkila Patricia J
Published: September 2006

Although proteins are essential components of all aspects of cell structure and function, they are not sufficient for their own propagation. Instead, the information necessary to specify each individual protein is stored in nucleic acids. The ‘central dogma’ of molecular biology states that sequence information can be transferred among nucleic acids, and from nucleic acids to proteins, but sequence information cannot be transferred among proteins, or from proteins to nucleic acids.
Chromosome Function: Sex Differences
Authors: Wolfner Mariana F
Published: September 2006

The distinct development of females and males is usually the consequence of differences in their sex chromosome constitution. To compensate for differences in sex chromosome make‐up, the sexes adjust the expression of sex‐linked genes. Some inheritance patterns depend on the sex or sex chromosome make‐up of a parent.
Genetic and Physical Map Correlation
Authors: Paz Margie M , Shoemaker Randy C
Published: September 2006

Genetic and physical maps provide a picture of the linear arrangement of genes and DNA markers on a chromosome. The relative distances between positions on a genetic map are calculated using recombination frequencies; a physical map is based on the actual number of nucleotide pairs between loci.
Mutations and the Genetic Code
Authors: De Boer Johan G
Published: September 2006

Mutations may change the coding function of the genome. The outcome of a mutation depends on the type of change and its location within or near genes.
Nonsense Mutations and Suppression
Authors: Herrington Muriel B
Published: September 2006

A nonsense mutation occurs when a codon that codes for an amino acid is changed to a chain‐termination codon. Informational suppression of a nonsense mutation occurs when changes in the translation apparatus enable the cell to insert an amino acid in response to the nonsense codon, resulting in a wild‐type or near wild‐type phenotype.
Neural Development: bHLH Genes
Authors: Vetter Monica , Harris William
Published: September 2006

Transcription factors of the basic helix‐loop‐helix (bHLH) class are involved in the determination of precursor cells towards neural (proneural) and other cell fates. The proneural members of this class constitute a particular subset of bHLH proteins that seem to be arranged in a cascade that affects different stages of neuronal commitment.
Semaphorins
Authors: Pasterkamp R Jeroen
Published: September 2006

The semaphorins are a family of intercellular signalling proteins known to deliver guidance cues to growing axons during development. Semaphorins bind with high affinity to at least two distinct receptor families, the neuropilins and plexins.
DNA
Chemical Instability
Authors: Poinar Hendrik
Published: September 2006

DNA is a relatively unstable molecule that undergoes hydrolytic, oxidative and nonenzymatic degradation. Its instability places limitations on its survival in the geosphere yet enables its rapid repair and turnover in our cells.
Somatic Hypermutation in Antibody Evolution
Authors: Storb Ursula
Published: September 2006

B lymphocytes activated by antigen and T lymphocytes initiate germinal centres in lymphoid tissues and hypermutate the variable region of their expressed immunoglobulin genes. The mechanism of this somatic hypermutation process depends on transcription. In chicken and rabbits, immunoglobulin gene mutations are created by gene conversion in a process that may have some relationship to cassette switching hypervariation in trypanosomes.
Housekeeping Genes
Authors: Mahadevappa Mamatha , Warrington Janet A
Published: September 2006

Housekeeping genes are those genes that encode proteins that carry out basic cellular maintenance functions and are required for cell survival and successful completion of the cell cycle.
Transmembrane Signalling
Authors: Holland Katalin A , Holland I Barry
Published: September 2006

Surface protein receptors detect a wide variety of different external signal molecules, inducing a resulting change in the cytoplasmic domain of a receptor, which activates an associated response regulator to transcribe a specific gene. In this way, the cell responds appropriately and uniquely to specific signals.
Bacterial Transcription Regulation
Authors: Müller‐Hill Benno
Published: September 2006

Escherichia coli
and possibly all other bacteria regulate transcription predominantly at the stage of initiation by repressors and/or activators.
Escherichia coliLactose Operon
Authors: Ullmann Agnes
Published: September 2006

The study ofEscherichia colilactose operon laid the foundation of modern molecular biology. It contributed to the elaboration of the concept of genetic regulation, to discover messenger RNA and to provide tools to a wide range of current applications in many fields of biology.
DNA Looping and Transcription Regulation
Authors: Lewis Dale EA , Adhya Sankar
Published: September 2006

DNA loops, formed by the association of two proteins while bound to spatially separated specific DNA sites, control gene transcription negatively or positively. DNA looping sometimes needs an architectural protein, which acts by bending the DNA segment that loops.