bluuebunny/crossref_metadata_2025 huggingface dataset:
Fine‐scale ultralow‐velocity zone structure from high‐frequency seismic array data
Authors: Rost Sebastian , Garnero Edward J. , Williams Quentin
Published: September 2006

Variability of core‐mantle boundary (CMB) structure is imaged at the kilometer to tens of kilometers scale by intensive waveform modeling of the ScP phase. Recordings of earthquakes in the Tonga‐Fiji subduction zone from the small‐aperture (10 km), high‐frequency (∼2–4 Hz) Alice Springs Array in central Australia are used to document anomalous ScP waveform variations due to the presence of an ultralow‐velocity zone (ULVZ) at the CMB. These data expand coverage from previous results using the Warramunga Array, which is located slightly to the north, and indicate the existence of a geographically confined ULVZ at the CMB, roughly 100 km in lateral extent, south of New Caledonia and east of Australia. Synthetic modeling indicates seismic velocity reductions of ∼8% and ∼24% for P wave and S waves, respectively, and a well‐constrained density increase of ∼10% in a ∼8.5 km thick layer above the CMB. This ULVZ patch is well explained by an elevated iron content of partially molten mantle material, likely present as divalent oxidized iron in the low spin state: The properties of such an iron‐enriched assemblage are consistent with both an elevated density and bulk modulus of this region, as are dictated from our best fit seismic results. Furthermore, a positive velocity gradient within the ULVZ may be present, which need not be associated with a decrease in melt content within this region but could rather be associated with a shift in the textural distribution of melt within the ULVZ.
On the simulation of winter precipitation types
Authors: Thériault J. M. , Stewart R. E. , Milbrandt J. A , Yau M. K.
Published: September 2006

Winter storms produce major problems for society, and the key responsible factor is often the varying types of precipitation. The objective of this study is to better understand the formation of different types of winter precipitation (freezing rain, ice pellets, snow, slush, wet snow and refrozen wet snow) within the varying and interacting environmental conditions in many winter storms. To address this issue, a one‐dimensional cloud model utilizing a double‐moment bulk microphysics scheme has been developed. Temperature and moisture profiles favorable for the formation of different winter precipitation types were varied in a systematic manner in an environment where snow is falling continuously through a temperature inversion. The ensuing precipitation evolved as a result of the variations in atmospheric temperature and moisture arising from phase changes such as melting and freezing. This study underlines the often complex manner through which different precipitation types form. It also demonstrates that the formation of semimelted particles can have a profound effect on the evolution of precipitation types aloft and at the surface. Furthermore, some types of precipitation only form within a narrow range of environmental conditions.
Does the Last Glacial Maximum constrain climate sensitivity?
Authors: Crucifix M.
Published: September 2006

Four simulations with atmosphere‐ocean climate models have been produced using identical Last Glacial Maximum ice sheets, topography and greenhouse gas concentrations. Compared to the pre‐industrial, the diagnosed radiative feedback parameter ranges between −1.30 and −1.18 Wm−2K−1, the tropical ocean sea‐surface temperature decreases between 1.7 and 2.7°C, and Antarctic surface air temperature decreases by 7 to 11°C. These values are all compatible with observational estimates, except for a tendency to underestimate the tropical ocean cooling. On the other hand, the same models have a climate sensitivity to CO2 concentration doubling ranging between 2.1 and 3.9 K. It is therefore inappropriate to simply scale an observational estimate of LGM temperature to predict climate sensitivity. This is mainly a consequence of the non‐linear character of the cloud (mainly shortwave) feedback at low latitudes. Changes in albedo and cloud cover at mid and high latitudes are also important, but less so.
Amine Neurotransmitters
Authors: Pearl Sandra M , Zigmond Michael J
Published: September 2006

Biogenic amines can serve as neurotransmitters, released from one nerve to act on another. Amine neurotransmitters, such as dopamine, serotonin, norepinephrine and epinephrine are important in many physiological functions including sleep, arousal, reinforcement and regulation of heart rate and blood pressure.
Amyotrophic Lateral Sclerosis
Authors: Festoff Barry W
Published: September 2006

Amyotrophic lateral sclerosis is a heterogeneous
neurodegenerative syndrome that has been described in the medical literature
for 150 years. Numerous theories of cause and pathogenesis have been
advanced but specific mechanisms have not yet been established. What is highly
likely is that numerous injurious agents can precipitate the cascade of events
that results in this well‐known syndrome. In the absence of knowing specific
cause(s), understanding this pathogenetic mechanism may be a target for novel
drug discovery efforts.
Auditory Processing
Authors: Forsythe Ian D
Published: September 2006

Sound is encoded as action potential trains by the cochlea and transmitted along the 8th nerve into the cochlear nucleus. Central auditory processing exemplifies several general principals of sensory neuronal conduction and control. Information is processed in parallel, with subdivisions of the auditory pathway adapted for specialized feature extraction and it is hierarchical. The temporal properties of sound mean that the preservation of timing information during auditory processing is of fundamental importance.
Brain Imaging: Observing Ongoing Neural Activity
Authors: DiGirolamo Gregory J , Clegg Benjamin A
Published: September 2006

The methods available to observe ongoing brain activity during human cognition include functional magnetic resonance imaging (fMRI), positron emission tomography (PET), event‐related electrical potentials (ERPs), magnetoencephalography (MEG) and event‐related optical imaging (EROS). They measure changes in either blood flow or the electrical or magnetic signals that emanate from the brain during human thought and emotion.
Cerebellar Plasticity
Authors: Ito Masao
Published: September 2006

Plasticity has been deemed as one of the characteristic functional features of the cerebellum based on classical observations of various compensation phenomena that follow cerebellar lesions. Advances in neurophysiology and computational neuroscience have yielded a new interpretation of the cerebellar plasticity, that it reflects the major mechanism of motor learning to acquire skills through repeated exercise. Mechanisms of motor learning have been investigated extensively in various simple forms of motor learning including the vestibuloocular reflex (VOR) adaptation. Synaptic plasticity, termed long‐term depression (LTD), has been identified in the cerebellum as a core process of motor learning.
Protein Synthesis in Neurons
Authors: Fallon Justin R , Taylor Aaron B
Published: September 2006

Neurons employ regulatory mechanisms at every step in the process of producing functional proteins. These mechanisms interact with extracellular signals to achieve spatially and temporally localized protein synthesis.
Voltage‐gated Potassium Channels
Authors: Heinemann Stefan H , Hehl Solveig
Published: September 2006

Voltage‐gated potassium channels are oligomeric membrane proteins that form ion pores highly selective for K
+
ions. Upon depolarization of the cell membrane, these channel proteins undergo molecular rearrangements leading to rapid activation, i.e. opening of the channels and, in some cases, subsequent inactivation.
Rhodopsin
Authors: Hargrave Paul A
Published: September 2006

Rhodopsin is the light‐sensitive protein of photoreceptor cells in the retina. It consists of a protein, opsin, linked to the 11‐cisisomer of vitamin A aldehyde (retinal), which carries out its function of transducing a light signal to a neural signal via a G‐protein cascade.
Schwann Cells
Authors: Scherer Steven S
Published: September 2006

Schwann cells are the glial cells of the peripheral nervous system. They form myelin sheaths, which are essential for saltatory conduction in normal nerves, and promote axonal regeneration in damaged nerves. Myelinating Schwann cells are selectively vulnerable to certain inherited diseases.
Olfaction
Authors: Breer Heinz
Published: September 2006

Olfaction, the ability to recognize and discriminate myriad airborne molecules with great accuracy and sensitivity, is one of the most remarkable but least understood senses. It permits continuous monitoring of the surroundings for small volatile molecules, including chemical signals that identify territories, food, predators and mates; thus, olfaction plays a key role in survival and adaptation in the animal world.
Sensory Transduction Mechanisms
Authors: Hart Anne , Sengupta Piali
Published: September 2006

Sensory transduction mechanisms function to translate sensory
signals from the external environment into responses by the organism.
Brain Evolution and Comparative Neuroanatomy
Authors: Butler Ann B
Published: September 2006

The central nervous system has changed over the course of time independently in different lineages of animals. The broad array of variation in nervous system structure reflects the diversity of successful niches and lifestyles available in the biological world.
Neurons and Neural Networks: Computational Models
Authors: Nadim Farzan , Manor Yair
Published: September 2006

Mathematical techniques can be used to build abstract models of the electrical signalling in single neurons and among neurons in a network. These models can be simulated using a computer.
Caenorhabditis elegans
Nervous System
Authors: Li Chris
Published: September 2006

The development, differentiation and function of the
Caenorhabditis elegans
nervous system is understood in great detail. With the mass of molecular and cellular data available this small nematode is a powerful tool for research in the neurosciences.
Sleep
Authors: Steriade M
Published: September 2006

Sleep comprises two distinct stages: REM sleep and resting sleep.
Somatosensory Systems
Authors: Goodwin Antony W
Published: September 2006

Sensations of touch, temperature, pain, and movement of joints
may be perceived from all parts of the body. Specialized receptor cells
convert the stimuli producing such sensations into electrical signals that are
processed in the somatosensory pathways of the nervous system.
Heterosynaptic Modulation of Synaptic Efficacy
Authors: Phares Gregg A , Byrne John H
Published: September 2006

Heterosynaptic modulation of synaptic efficacy occurs when the activity of a modulatory neuron induces a change in synaptic efficacy between another neuron and its target cell.
Motor Output from the Brain and Spinal Cord
Authors: Berkowitz Ari
Published: September 2006

Skeletal muscles are activated by motor neurons in the spinal cord and brainstem. Other neurons in the spinal cord, reticular formation, vestibular nuclei, red nucleus, superior colliculus, cerebellum, basal ganglia and cerebral cortex control movements by direct or indirect inputs to motor neurons.
Muscarinic Acetylcholine Receptors
Authors: Nathanson Neil M
Published: September 2006

Muscarinic acetylcholine receptors play a key role in the regulation of signal transduction in the central and peripheral nervous systems.
Passive Propagation of Electrical Signals
Authors: Elmslie Keith S
Published: September 2006

The subthreshold potentials (too small to generate action potentials) can be passively propagated along the membrane. The time course, speed and distance travelled of these propagated potentials depend on three properties: membrane resistance, membrane capacitance and axial resistance.
Stroke
Authors: Auer Roland N
Published: September 2006

Blood vessels supplying the brain can be either blocked or broken, giving rise to the two kinds of stroke: infarcts and haemorrhages. The symptoms and their permanence depend on how much brain tissue is destroyed and in what location.
Synapses
Authors: Schweizer Felix E
Published: September 2006

Synapses are the connection sites between nerve cells and their targets, either other nerve cells or effector cells such as muscle. The transfer of information across synapses, called synaptic transmission, is a tightly regulated process that can be modulated.
Synaptic Vesicle Proteins
Authors: Bean Andrew J , Vida Thomas A
Published: September 2006

Synaptic transmission underlies much of interneuronal communication and is essential for nervous system function. Small vesicles, initially observed by morphological methods, and abundant in the nerve terminal, are filled with neurotransmitters and fuse with the plasma membrane, enabling secretion into the synaptic cleft. In the last 10 years, molecular details of the synaptic vesicle life cycle have emerged, allowing a more complete understanding of neurotransmitter secretion.
Opiates
Authors: Dickenson Tony
Published: September 2006

Morphine and the opiates are some of the most valuable drugs in medicine and their actions can now be explained in terms of their acting as agonists at one of the four opiate receptors found in the brain, spinal cord and peripheral nervous system. All four receptors are inhibitory.
Postsynaptic Membranes at the Neuromuscular Junction: Molecular Organization
Authors: Cartaud Jean , Kordeli Ekaterini , Cartaud Annie
Published: September 2006

Synaptic transmission at the neuromuscular junction requires the
precise spatial registration and a high degree of local molecular
differentiation of both presynaptic and postsynaptic membrane domains. At
these two sites, the accumulation of various proteins, particularly ion
channels, is responsible for the regulated secretion of the neurotransmitter
by the nerve terminal and for the subsequent depolarization of the
postsynaptic membrane.
Protein Phosphorylation and Long‐term Synaptic Plasticity
Authors: Barria A , Derkach V , Soderling TR
Published: September 2006

Learning and memory are complex biological processes that
utilize multiple mechanisms in the brain. Some of these mechanisms, which
involve phosphorylation of key regulatory brain proteins, have been identified.
Adrenaline and Noradrenaline: Introduction
Authors: Stanford S Clare
Published: September 2006

The catecholamines, noradrenaline (norepinephrine) and adrenaline (epinephrine), are found both in the adrenal gland and in neurons which have distinct distributions throughout the nervous system. The synthesis and release of these catecholamines are tightly regulated to ensure their sustained influence on internal body state and brain functions such as arousal and mood.
Bacterial Cell Wall
Authors: Beveridge Terry J
Published: September 2006

Bacterial walls are constructed from a variety of macromolecules and polymers to provide an outer skin around the protoplast, encompassing the cell. In Gram‐positive bacteria, the cell wall consists of peptidoglycan and associated secondary polymers, whereas in Gram‐negative bacteria it consists of an outer membrane and an underlying thin peptidoglycan layer.
Bacterial Intracellular Membranes
Authors: Stolz John F
Published: September 2006

Bacterial intracellular membranes differ widely in their functions, topology and composition and include the thylakoids of cyanobacteria and chloroxybacteria, the intracytoplasmic membranes of purple bacteria and chemoautotrophic bacteria, and the membranes associated with the chlorosomes of green bacteria.
Algal Spores
Authors: Maggs Christine A , Callow Maureen E
Published: September 2006

Algal spores are cells that can reproduce independently (i.e. asexually) an individual of that species. In their turbulent hydrodynamic environment, dispersal, adhesion and recruitment are moderated by a range of environmental cues and signals.
Biogeography of Marine Algae
Authors: Garbary David J
Published: September 2006

Marine algal biogeography is concerned with the distribution of marine algal species and the underlying ecophysiological, evolutionary and human causes of these distributions.
Algal Ecology
Authors: DeWreede Robert E
Published: September 2006

Algal ecology is the study of the distribution and abundance of algae, of the environment in which they exist, and of the interactions between the algae and with other organisms.
Algal Taxonomy: Historical Overview
Authors: Moestrup Øjvind
Published: September 2006

Taxonomy deals with taxa at all levels from species or below to the highest levels (families, orders, divisions, etc.).
Acidophiles
Authors: Norris Paul R
Published: September 2006

Phylogenetically diverse acidophiles (affiliated with various divisions of the Bacteria and Archaea) grow at below pH 3 while generally maintaining a cytoplasmic pH relatively close to neutrality. They are found principally in natural and industrial environments where sulfuric acid is generated from oxidation of sulfur or sulfides.
Bacterial Ecology
Authors: Fenchel Tom
Published: September 2006

Bacterial ecology is concerned with the interactions between bacteria and their environments and with the role of bacteria in biogeochemical element cycling.
Biofilms
Authors: Fletcher Madilyn , Decho Alan W
Published: September 2006

The attachment of bacteria to surfaces, followed by their growth and the production of extracellular polymers, results in the formation of a bacterial biofilm. The biofilm community is a complex assemblage of different metabolic types of microorganisms, which may interact through a variety of physiological, genetic and behavioural processes.
Circadian Rhythms in
Neurospora
Authors: Dunlap Jay C
Published: September 2006

Over the past decade, genetic and molecular analysis of the circadian system of Neurospora has uncovered a number of paradigms now seen to be universal in the operation of circadian rhythms.
Fungal Pathogens of Nonhuman Animals
Authors: Smith John MB
Published: September 2006

Fungal infections of nonhuman animals, including domestic companion and farm animals, fish and other aquatic vertebrates are common and involve an increasing variety of environmental and occasionally endogenous fungi. In most cases, the causal fungi are of low virulence and require that the host be immunologically compromised in order to initiate active disease. Methods of control and possible treatment of these diseases are poorly understood.
Hyphae
Authors: Ross Ian K
Published: September 2006

Fungal hyphae are cylindrical, apically extending, branching cells that are the basic units of the modular organisms called filamentous fungi. They have the potential to be highly plastic in form and function and, although behaving as coordinated individuals during vegetative growth and assimilation, can differentiate into highly regulated multicellular structures containing a wide variety of tissues and cell types.
Fungi: Ecological Importance and Impact on Humans
Authors: Kendrick Bryce
Published: September 2006

Fungi play vital though generally inconspicuous roles in the biosphere, some of which affect human health in various ways.
Nematophagous Fungi
Authors: Nordbring‐Hertz Birgit , Jansson Hans‐Börje , Tunlid Anders
Published: September 2006

Nematophagous fungi are microfungi that can capture, kill and digest nematodes. They use special mycelial structures, so‐called traps, or spores to trap vermiform nematodes or hyphal tips to attack nematode eggs and cysts before penetration of the nematode cuticle, invasion and digestion.
Yeast Artificial Chromosomes
Authors: Bruschi Carlo V , Gjuracic Kresimir
Published: September 2006

Yeast artificial chromosomes are shuttle‐vectors that can be amplified and modified in bacteria and employed for the cloning of very large DNA inserts (up to 1–2 megabase pairs) in the yeast
Saccharomyces cerevisiae
.
Archaeal Cells
Authors: Beveridge Terry J
Published: September 2006

Archaea are prokaryotic cells and belong to a separate domain to that of Bacteria. They have a simple cell structure and could resemble the most primitive cells which arose more than 3000 million years ago.
Halophiles
Authors: DasSarma Shiladitya , Arora Priya
Published: September 2006

Halophiles are salt‐loving organisms that inhabit hypersaline environments. They include mainly prokaryotic and eukaryotic microorganisms with the capacity to balance the osmotic pressure of the environment and resist the denaturing effects of salts.
Hydrothermal Vent Communities
Authors: Canganella Francesco
Published: September 2006

Deep‐sea hydrothermal vents are hydrogeological phenomena occurring on the deep ocean bottom, wherever it is a tectonically active area and heated waters reach the seafloor with significant temperatures and pressures. Specific animal communities are strongly associated with these hydrothermal areas, and unique trophic relationships are established among chemolithotrophic bacteria, clams and mussels.
Phototaxis: Microbial
Authors: Fisher Paul R
Published: September 2006

Phototaxis in its broadest sense is light‐regulated movement of motile organisms (microorganisms in the case of microbial phototaxis), usually resulting in their attraction to (positive phototaxis) or avoidance of (negative phototaxis) illuminated regions.
Microorganisms in High‐temperature Sulfur Environments
Authors: Stetter Karl O
Published: September 2006

Sulfur‐rich high‐temperature environments such as solfataric fields, hot springs and ‘black smokers’ provide habitats for microbial life at the upper temperature border. During recent years, such regions have yielded hyperthermophilic bacteria and archaea that grow optimally at temperatures above 80°C, some even above 100°C.
Antiviral Drugs
Authors: Oxford John S
Published: September 2006

Antiviral drugs have now been developed against influenza, herpes and human immunodeficiency viruses. Drug resistance could be a practical problem but should stimulate the wider search for new drugs using compound libraries, molecular technology and particularly X‐ray crystallography.
Enteroviruses
Authors: Tracy Steven M , Chapman Nora M , Gauntt Charles J
Published: September 2006

Enteroviruses are common, single‐stranded positive‐sense RNA genome human viruses that cause a variety of benign to serious disease.
Human Pathogenic Viruses
Authors: McKee Tom , Minson Tony
Published: September 2006

Human pathogenic viruses are submicroscopic infectious agents that multiply only inside living cells and which cause disease in humans.
Rabies Virus
Authors: Hanlon Cathleen A , Orciari Lillian A
Published: September 2006

Rabies is an acute fatal encephalomyelitis, caused by a group of genetically related lyssaviruses. The primary sources of rabies are major animal reservoirs in the orders Chiroptera and Carnivora, although this deadly zoonosis may affect all mammals, including humans.
Virology
Authors: Brown Jay C
Published: September 2006

Viruses are small infectious agents that are able to replicate only in living cells. They are known for their ability to produce disease in their animal and plant hosts, and they have played a prominent role in the recent expansion of knowledge in the fields of cell and molecular biology.
Archaea
Authors: König Helmut
Published: September 2006

Archaea represent one of the three domains of life (the other two being Bacteria and Eukarya). Their separate phylogenetic position has been confirmed by small subunit rRNA sequence analysis and also by investigation of their physiological, biochemical and genetic features.
Codes of Nomenclature
Authors: Krichevsky Micah I
Published: September 2006

Codes of Nomenclature are the agreed conventions for naming biological groups. The various Codes define the rules for constructing the names of biological entities.
Progenotes
Authors: Hartman Hyman
Published: September 2006

The progenote is a hypothetical candidate for the last universal cellular ancestor. There are two major conjectures associated with this entity: (1) the progenote's genome is based on RNA rather than DNA and (2) the replication, transcription and translation of this RNA organism had a much higher error rate than the ensuing DNA‐based cells.
Immunity to Infection
Authors: Pedersen Anders Elm
Published: September 2006

The immune system comprises the innate immune response and the adaptive immune system. Innate immunity is an immediate response to a pathogen but has limited capacity to recognize antigens. In contrast, induction of the adaptive immune response takes several days but it has the capacity to recognize an almost unlimited number of antigens and also comprises memory. Innate and adaptive immune responses cooperate during an infection and are constantly regulated to mount the most appropriate response to an antigen.
Immunity to Parasitic Worms
Authors: Klion Amy D , Nutman Thomas B
Published: September 2006

Helminth infection provides a unique challenge to the host immune system. Not only are helminths complex multicellular organisms, but they have intricate life cycles with multiple developmental stages, several of which may coexist in the infected host.
Immune Defence: Role of Reactive Nitrogen Intermediates
Authors: Wink David A , Citrin Deborah , Vitek Michael P , Colton Carol , Pacelli Roberto , Ogawa Rygeio , Thomas Douglas D , Miranda Katrina M , Espey Michael G
Published: September 2006

An exploration of the different facets of the NO redox chemistry in the immune response to different pathogens.
Immune Response: Evasion and Subversion by Pathogens
Authors: Milon Geneviève , David Peter
Published: September 2006

Pathogenic microorganisms may evade rapid clearance by effectors of the immune system of the hosts they encounter, or they may subvert the regulatory pathways of the immune system of the hosts. These two processes are essential for microorganisms' fitness, transmissibility and perpetuation, the very essence of host‐dependent/parasitic microorganisms.
Antibiotic Molecules: Intracellular
Authors: Borregaard Niels
Published: September 2006

Intracellular antibiotic molecules are the essential components of innate, i.e. nonadaptive, immunity. Some are stored proteins with highly specific antibiotic activity, others are stored peptides that have a broad antibacterial spectrum, yet others are short‐lived molecular reagents that are generated by specific activation of phagocytes, the cells equipped especially for microbicidal activity
Acute‐phase Proteins
Authors: Gabay Cem , Kushner Irving
Published: September 2006

Acute‐phase proteins form part of the systemic acute‐phase response which accompanies inflammation. Their synthesis by hepatocytes is primarily regulated by inflammation‐associated cytokines and their presumed functions are highly variable and diverse.
Antigens: Thymus‐dependent
Authors: Bachmann Martin F
Published: September 2006

B cells secrete antibodies that mediate protection against a great variety of pathogens. Two factors govern the strength of B‐cell responses: the degree of receptor crosslinking on B cells and the presence of cognate T help.
Chemotaxis: Role in Immune Response
Authors: Luster Andrew D
Published: September 2006

Chemotaxis is defined as the unidirectional movement of a cell in response to a chemical gradient in the direction from a low to a high concentration of chemoattractant.
Complement
Authors: Sunyer J Oriol , Lambris John D
Published: September 2006

The mammalian complement system consists of a complex group of more than 30 soluble proteins and receptors that play an important role in innate and acquired host defence mechanisms against infection, and participate in various immunoregulatory processes. The functions mediated by complement activation products include phagocytosis, cytolysis, inflammation, solubilization of immune complexes and promotion of humoral immune responses.
Complement: Terminal Pathway
Authors: Sodetz James M , Plumb Mnason E
Published: September 2006

Terminal pathway of complement refers to the sequence of interactions between components C5b, C6, C7, C8 and C9 which lead to the production of a ‘membrane attack complex’ that has the ability to disrupt cell membranes.
Lymph Nodes
Authors: Weiss Lawrence M
Published: September 2006

The lymph nodes are numerous encapsulated structures occurring in mammalians along the lymphatics. They contain lymphoid cells with a precise microanatomy organized to react to a variety of antigens via humoral and cellular immune responses.
Transfer
RNA
Structure
Authors: Westhof Eric , Auffinger Pascal
Published: September 2006

Transfer ribonucleic acid (tRNA) molecules that participate in the elongation step of protein synthesis on the ribosome have a conserved secondary structure, known as the cloverleaf, and fold into a common three‐dimensional architecture.
mRNA Stability
Authors: Lundberg Urban , von Gabain Alexander
Published: September 2006

The steady‐state level of a messenger ribonucleic acid (mRNA) is determined by both its rate of synthesis and degradation; in addition, the half‐life of individual mRNAs can alter in response to environmental changes.
Ribosomal Proteins: Structure and Evolution
Authors: Wittmann‐Liebold Brigitte , Graack Hanns‐Rüdiger
Published: September 2006

Ribosomal proteins (r‐proteins) are constituents of the ribosome, the organelle in the cell that provides the translation of the genetic message into proteins. The r‐protein number varies from about 55 to more than 70 in different organisms. Together with 3–4 ribosomal RNA strains (rRNAs) they constitute the two subunits of the ribosome, the small and the large subunits. By specific interaction the r‐proteins are bound to the rRNAs and the neighbouring proteins of the organelle and constitute together the protein biosynthesis machinery of the cell.
r
RNA
Structure
Authors: Malhotra Arun
Published: September 2006

Ribosomal RNAs (rRNA) are essential components of ribosomes which are responsible for protein synthesis in all living cells. rRNA structure can be described at several levels – at the level of their primary sequences and secondary structures, as well as in terms of their tertiary folds of macromolecules within the ribosomal subunits.
DNA
Repair
Authors: Posnick Lauren M , Samson Leona D
Published: September 2006

When the DNA in cells is damaged by chemical or physical agents, such as ultraviolet light, the damage can lead to DNA mutations or even cell death. Cells use various DNA‐repair proteins to fix any damage and to prevent damage‐induced mutations and killing.
DNA Damage
Authors: Doetsch Paul W
Published: September 2006

Various biochemical and physical events alter the structure and properties of DNA and convert it into forms that can have deleterious biological consequences for cells. Technologies exist for the sensitive detection and measurement of DNA damage in cells exposed to various agents.
Nucleotide Excision Repair in Bacteria
Authors: Grossman Lawrence , Kovalsky Oleg
Published: September 2006

Nucleotide excision repair removes a wide variety of damages from bacterial genomes through a set of coordinated enzymatic reactions carried out by multiprotein complexes. It is coupled to other cellular processes, notably transcription.
DNA Mismatch Repair: Eukaryotic
Authors: Hays John Bruce
Published: September 2006

In both prokaryotes and eukaryotes, highly‐conserved mismatch‐repair systems both correct DNA replication errors, by coupling recognition of DNA mismatches to identification and excision of the mutated nascent DNA, and interact with recombination mismatches and a variety of DNA lesions. Evolution of single prokaryotic recognition (MutS) and coupling (MutL) proteins into multiple specialized eukaryotic proteins has accompanied expansion of their genomic‐stability functions.
Eukaryotic Recombination: Initiation by Double‐strand Breaks
Authors: Richardson Christine , Jasin Maria
Published: September 2006

A double‐strand break in one deoxyribonucleic acid (DNA) double helix, possibly caused by DNA damaging agents such as ionizing radiation or normal metabolic processes, stimulates repair by a pathway of recombination that uses a second unbroken DNA double helix containing homologous sequences as a donor of genetic information to restore the intact DNA structure.
Homologous Genetic Recombination in Eukaryotes
Authors: Sung Patrick
Published: September 2006

In eukaryotes, homologous recombination is mediated by genes of the
RAD52
epistasis group. Several products of the
RAD52
group genes function together to catalyse the homologous DNA pairing and strand exchange reaction that establishes a stable linkage between the recombining chromosomes.
Rec
FOR
Protein
Authors: Sandler Steven J
Published: September 2006

In
Escherichia coli
the
recF
,
recO
and
recR
(
recFOR
) proteins interact with DNA, single‐stranded DNA‐binding (SSB) protein and RecA protein to facilitate recombinational repair (also called post‐replication repair and daughter‐strand gap repair) of DNA damage encountered by a DNA replication fork. The
recF
,
recO
and or
recR
genes have been found in 36 different types of bacteria ranging from the kingdoms of proteobacteria to aquificales.
Developmentally Programmed
DNA
Rearrangements
Authors: Fillingham Jeffrey S , Pearlman Ronald E
Published: September 2006

Developmentally programmed DNA rearrangements are structural reorganizations of the genome that occur reproducibly during the ontogeny of a variety of organisms. In the majority of cases programmed DNA rearrangements function to alter gene expression. However in a few cases no function to large‐scale developmentally programmed DNA rearrangements has yet been ascribed.
Haem Structure and Function
Authors: Vicente Maria da Graça H , Smith Kevin M
Published: September 2006

Haems are the vital catalysts in a large number of biological processes, including oxygen transport, oxygen storage, electron transport and oxygenation. Haem proteins contain an iron complex of porphyrin, usually protoporphyrin IX, and exist in haemoglobin, myoglobin, cytochromes, catalases, peroxidases, oxygenases and oxidases.
Glycolytic Enzymes
Authors: Michels Paul AM , Verlinde Christophe LMJ
Published: September 2006

Glycolysis, the breakdown of glucose, is a central metabolic
process in all organisms. The ten enzymes of this pathway convert the six‐carbon sugar, glucose, into two pyruvate molecules, a three‐carbon compound, with the concomitant net production of two ATP molecules.
Quantification of Metabolic Fluxes
Authors: Gombert Andreas Karoly , Nielsen Jens
Published: September 2006

The phenotype of an organism grown under defined environmental conditions may be characterized by the fluxes carried out at each individual reaction in the organism's metabolic network. Metabolic fluxes are nonmeasurable quantities, but they can be quantified using a combination of specific measurements and mathematical modelling.
Ground State Destabilization
Authors: Anderson Vernon E
Published: September 2006

Ground state destabilization is a thermodynamic concept suggesting that there is an increase in energy in going from one state to another. This concept helps to explain the efficiency of enzyme‐catalysed reactions, as when the substrate binds to the active site of the enzyme there is a destabilization of the substrate. The effect of this destabilization is to reduce the activation energy of a reaction, and so make the catalysis more efficient.
Fatty Acid Oxidation
Authors: Morio Beatrice , Yeckel Catherine W , Wolfe Robert R
Published: September 2006

The regulation of fatty acid oxidation is multifaceted, but the oxidation of fatty acids can only proceed once fatty acids gave gained entry to mitochondria. The mechanisms of transmembrane and transcellular movement of fatty acids may involve a number of fatty acid‐binding proteins. The gateway into mitochondria may be regulated by carnitine palmitoyltransferase.
Lipid Bilayers
Authors: Raudino Antonio , Sarpietro Maria Grazia
Published: September 2006

Lipid bilayer is the most simple model of the cell membrane which retains many of its properties even in the absence of proteins. Its formation, structure and properties rely on a subtle combination of different physical forces as well as on the unique chemical nature of its components: the lipid molecules.
Flavin Coenzymes
Authors: Ghisla Sandro , Edmondson Dale E
Published: September 2006

Flavins are yellow chromophores that are widespread in organisms from bacteria to humans and are essential for practically all metabolic processes. As cofactors flavins are distinguished by the ability to catalyse a wide variety of different processes.
G Proteins
Authors: Mesters Jeroen R , Hogg Tanis , Hilgenfeld Rolf
Published: September 2006

The G proteins, or GTP‐binding proteins, can be classified into
three major groups: the large mammalian Gαβγ heterotrimers,
the small Ras and Ras‐like GTPases, and the intermediate‐sized GTPases such as
elongation factors Tu (EF1A) and G (EF2). All G proteins function as molecular
switches controlled by a GTPase cycle, shuttling between an active GTP–Mg
2+
‐bound
form (the ‘on’ state) and an inactive GDP–Mg
2+
complex (the ‘off’ state).
Protein Kinases
Authors: Sowadski Janusz M , Epstein Linda F
Published: September 2006

Regulation of essential cellular processes, such as cell division, growth and death, are governed by protein kinases. These enzymes transfer phosphate from adenosine triphosphate (ATP) onto target proteins, thereby activating or deactivating them.
Amino Acid Cofactors
Authors: Davidson Victor L
Published: September 2006

Amino acid cofactors are typically metal or organic ions that are essential for electrophilic catalysis.
Photosystem II
Authors: Whitmarsh John , Govindjee
Published: September 2006

Photosystem II is a specialized protein complex that uses light energy to oxidize water, resulting in the release of molecular oxygen into the atmosphere, and to reduce plastoquinone, which is released into the hydrophobic core of the photosynthetic membrane. All oxygenic photosynthetic organisms, which include plants, algae and some bacteria, depend on photosystem II to extract electrons from water that are eventually used to reduce carbon dioxide in the carbon reduction cycle. The complex is composed of a central reaction centre in which electron transport occurs, and a peripheral antenna system which contains chlorophyll and other pigment molecules that absorb light.
Dynein and Kinesin
Authors: Bowman Aaron B , Goldstein Lawrence SB
Published: September 2006

The microtubule‐based motors of the kinesin and dynein superfamilies mediate intracellular transport and cilia/flagella motility within eukaryotic cells.
Ribosomal Proteins: Role in Ribosomal Functions
Authors: Stelzl Ulrich , Connell Sean , Nierhaus Knud H , Wittmann‐Liebold Brigitte
Published: September 2006

The assignment of individual ribosomal proteins to specific ribosomal functions is difficult due to the enormous cooperativity of the ribosome. However, the role of a few proteins have been clarified using various techniques. In particular, mutations altering ribosomal proteins and mediating resistance against antibiotics have provided important clues.
Recombinational DNA Repair in Bacteria: Postreplication
Authors: Rice Kevin P , Cox Michael M
Published: September 2006

Recombinational DNA repair represents the primary function for homologous DNA recombination in bacteria. Most of this repair occurs at replication forks that are stalled at sites of DNA damage.
Polysaccharides
Authors: BeMiller James N
Published: September 2006

Polysaccharides are polymers containing from 20 (usually >100) to as many as 60 000 monosaccharide units. Polysaccharides have a range of general structures (from linear to various branched structures) and shapes. They are structural components of cell walls of bacteria, fungi, algae and higher plants, are energy‐ and carbon‐storage substances, and serve various other functions as extracellular materials of plants, animals and microorganisms. They are the most abundant (by mass) of all organic substances in living organisms, comprising about two‐thirds of the dry weight of the total biomass. Some have commercial value as isolated substances.
Polysaccharides: Bacterial and Fungal
Authors: Sutherland Ian W
Published: September 2006

Microbial exopolysaccharides are the polysaccharides that are produced outside the cell wall by many microorganisms. Some are well‐established biotechnological products that are manufactured commercially from renewable resources to provide biodegradable alternatives to traditional plant and algal gums. Others have potentially useful physical or chemical properties, while a few possess valuable biological properties.
Peptidoglycan
Authors: Young Kevin D
Published: September 2006

Peptidoglycan is the rigid macromolecule that surrounds and protects individual bacterial cells. It defines cell shape and anchors extracellular organelles while remaining porous enough to admit essential nutrients and large compounds. Because it is unique to bacteria, peptidoglycan is one of the most valuable targets to which antibiotics may be directed.
Glycoproteins
Authors: Butters Terry D
Published: September 2006

Glycoproteins are proteins that contain covalently bound oligosaccharides. Although there are structural features of
N
‐ and
O
‐linked oligosaccharides common to all eukaryotes, species‐specific glycosylation reactions create a wide diversity of structures.
Lipids
Authors: Yeagle Philip L
Published: September 2006

The lipids of cell membranes are amphipathic molecules, having polar headgroups and hydrophobic hydrocarbon tails. They self‐assemble, according to the hydrophobic effect, to form bilayers, the fundamental architectural element of cell membrane structure. Membrane lipids exhibit a variety of headgroup structures and of hydrocarbon chain lengths (commonly 12 to 26 carbon atoms) and unsaturation (zero to 6 unconjugated double bonds) that determine the influence of these lipids on cell membrane properties.
Mammalian Embryo: Wnt Signalling
Authors: Takada Shinji
Published: September 2006

Wnt signalling is essential for various aspects of mouse development, including central nervous system development, gastrulation and organogenesis.
Virus Diseases of Tropical Crops
Authors: Thresh JM , Fargette Denis
Published: September 2006

Virus diseases are serious constraints on the productivity and profitability of a wide range of tropical crops.
Viruses and Plant Disease
Authors: Plumb Roger T
Published: September 2006

Viruses are sublight‐microscopic infectious particles, often spread by a range of invertebrate species, especially insects, that can cause disease in most plants. Plants can be killed but more often show a range of symptoms including leaf variegation, mottle, mosaic, distortion and stunting.
Lysogeny
Authors: Campbell Allan M
Published: September 2006

Lysogeny is the harbouring of a quiescent bacteriophage genome within the genome of a growing bacterial host.
Neuronal Subtype Identity Regulation
Authors: Reissmann Eva , Brivanlou Ali H
Published: September 2006

The generation of diverse neuronal cells in the nervous system is achieved through inductive interactions between neighbouring cells. This communication requires, at the same time, both the presence of secreted or membrane‐attached signals and the competence of affected cells to convert these signals into intracellular responses. Patterning events in the developing spinal cord is an example of inductive interactions in the formation of the vertebrate nervous system.
Neural Activity and the Development of Brain Circuits
Authors: Hohnke Carsten D , Sur Mriganka
Published: September 2006

The development of highly interconnected circuits in the brain relies on patterns of neural activity. These patterns produce a cascade of events that refine initially imprecise connectivity into precise circuits. The presence of neural activity is particularly important during well‐defined critical periods in early life.
Trophic Support
Authors: Davies Alun M
Published: September 2006

The survival of neurons in the developing vertebrate nervous system is dependent on the supply of one or more neurotrophic factors. There are several families of these proteins, which may act by a paracrine or autocrine route.
Escherichia coli
and the Development of Bacterial Genetics
Authors: Cupples Claire G
Published: September 2006

Bacterial and phage genetics have been central to development of the modern science of molecular biology. Molecular techniques such as genome sequencing will be instrumental in the bacterial genetics of the twenty‐first century.
Vertebrate Neurogenesis: Cell Polarity
Authors: Adams Richard J
Published: September 2006

The central nervous system of vertebrates contains an enormous number of cells. Virtually all of these cells are produced by a highly proliferative epithelium that lines the ventricles of the developing brain. We are now just beginning to understand the rules that govern the determination of fate in this process.
Conditional Lethal Mutations as Experimental Tools
Authors: Black A Kristine , Singh Shiva M
Published: September 2006

Conditional lethal mutations are changes in the sequence of genetic material, which kill the organism, but only when it faces certain environmental conditions; under other conditions, the organism can survive and grow. Such mutations are useful genetic markers for a variety of essential genes.
Mutagenesis Mechanisms
Authors: Cupples Claire G
Published: September 2006

Many types of DNA lesion cause mutations. Although mutations may be harmful to the individual cell, mutation in populations is valuable because it leads to genetic variation.
RNA Synthesis
Authors: Drapkin Ronny I , Reinberg Danny F
Published: September 2006

Transcription is the process of RNA synthesis in which the information stored in DNA is converted to RNA by an enzyme called RNA polymerase. Transcription constitutes a complex reaction whose essential features have been evolutionarily preserved from bacteria to mammals.
Transcription Activation at Bacterial Promoters
Authors: Busby Steve , Savery Nigel
Published: September 2006

Bacterial genomes encode thousands of proteins that are expressed in widely differing quantities. Moreover, the expression of many proteins is induced or repressed according to the particular circumstances of the bacterium. Much of this regulation is effected at the level of the initiation of transcription.
Substrate Binding to Enzymes
Authors: Pliška Vladimir K
Published: September 2006

Binding of a substrate to an enzyme is the first step of the interaction between substrate (ligand) and enzyme molecules that leads to the formation of an intermediate substrate–enzyme complex. The formation process is controlled mainly by diffusion and requires a structural complementarity between the enzyme and ligand.
Vitamin
K
‐dependent Carboxylase
Authors: Suttie John W
Published: September 2006

Proteins are posttranslationally modified by specific γ‐glutamyl carboxylation. It is believed this reaction is the only known metabolic role of the vitamin K‐dependent enzyme that carries out this carboxylation.
Regulatory Cascade
Authors: Lint Johan Van , Vandenheede Jackie R
Published: September 2006

An enzyme cascade is a regulatory system where one enzyme catalyses the covalent modification of another enzyme. Regulatory cascades are either unidirectional or cyclic; both types are important biological switches for the regulation of physiological processes.
Lysozyme
Authors: Imoto Taiji
Published: September 2006

Lysozymes are lytic enzymes that hydrolyse glycosidic bonds and are widely distributed in nature. Hen egg‐white lysozyme is the best‐characterized of all proteins and, as well as serving as a model protein for study, its antibacterial and immune function properties are exploited in medicines and food‐additives.
Messenger
RNA
in Eukaryotes
Authors: Kreivi Jan‐Peter , Petersen‐Mahrt Svend , Akusjärvi Göran
Published: September 2006

Posttranscriptional regulation of gene expression represents an important level at which eukaryotes can expand the coding capacity of their genomes. The concept that one gene makes one protein does not apply to higher eukaryotes. Thus, a eukaryotic cell can use alternative RNA splicing and alternative polyadenylation to produce hundreds or even several thousands of protein isoforms from a single gene.