Home About us Contact
|
Home About us Contact | ||
|
|
||
Structure-function Relationships (structure-function + relationships)
Selected AbstractsEmbryonic Staging System for the Black Mastiff Bat, Molossus rufus (Molossidae), Correlated With Structure-Function Relationships in the AdultTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2009Mark J. Nolte The helmeted appearance of the black mastiff bat, Molossus rufus, at embryonic stage 21 results from the anterior margins of the ears being progressively situated near the facial midline during development. Comparative bat embryology provides a foundation for understanding unique mammalian and chiropteran (bat) adaptations, such as the marked ability of M. rufus to use its compactly folded wings during terrestrial quadrupedal locomotion. See Nolte et al., on page 155, in this issue. [source] Combined Confocal Microscopy and Stereology: a Highly Efficient and Unbiased Approach to Quantitative Structural Measurement in TissuesEXPERIMENTAL PHYSIOLOGY, Issue 6 2002Katherine Howell Understanding the relationship of the structure of organs to their function is a key component of integrative physiological research. The structure of the organs of the body is not constant but changes, both during growth and development and under conditions of sustained stress (e.g. high altitude exposure and disease). Recently, powerful new techniques have become available in molecular biology, which promise to provide novel insights into the mechanisms and consequences of these altered structure-function relationships. Conventionally structure-function relationships are studied by microscopic examination of tissue sections. However, drawing conclusions about the three-dimensional structure of an organ based on this two-dimensional information frequently leads to serious errors. The techniques of stereology allow precise and accurate quantification of structural features within three-dimensional organs that relate in a meaningful way to integrated function. For example, knowledge of changes in the total surface area of the capillary endothelium in an organ can be related directly to changes in fluid filtration and permeability, or knowledge of total vessel length and mean radius allows deductions about vascular resistance. Confocal microscopy adds enormously to the power of stereological approaches. It reduces the difficulties and labour involved in obtaining suitable images. Moreover, when used in conjunction with new analytical software, it allows convenient application of stereology to small samples and those in which it is essential to maintain a specific orientation for interpretation. The information obtained will allow us to examine in a quantitative manner the altered structure-function relationships produced by manipulation of single genes and regulatory pathways in whole organisms. [source] Functional analysis of disease-causing mutations in human galactokinaseFEBS JOURNAL, Issue 8 2003David J. Timson Galactokinase (EC 2.7.1.6) catalyzes the first committed step in the catabolism of galactose. The sugar is phosphorylated at position 1 at the expense of ATP. Lack of fully functional galactokinase is one cause of the inherited disease galactosemia, the main clinical manifestation of which is early onset cataracts. Human galactokinase (GALK1) was expressed in and purified from Escherichia coli. The recombinant enzyme was both soluble and active. Product inhibition studies showed that the most likely kinetic mechanism of the enzyme was an ordered ternary complex one in which ATP is the first substrate to bind. The lack of a solvent kinetic isotope effect suggests that proton transfer is unlikely to be involved in the rate determining step of catalysis. Ten mutations that are known to cause galactosemia were constructed and expressed in E. coli. Of these, five (P28T, V32M, G36R, T288M and A384P) were insoluble following induction and could not be studied further. Four of the remainder (H44Y, R68C, G346S and G349S) were all less active than the wild-type enzyme. One mutant (A198V) had kinetic properties that were essentially wild-type. These results are discussed both in terms of galactokinase structure-function relationships and how these functional changes may relate to the causes of galactosemia. [source] Loss-of-function variants of the human melanocortin-1 receptor gene in melanoma cells define structural determinants of receptor functionFEBS JOURNAL, Issue 24 2002Jesús Sánchez Más The ,-melanocyte-stimulating hormone (,MSH) receptor (MC1R) is a major determinant of mammalian skin and hair pigmentation. Binding of ,MSH to MC1R in human melanocytes stimulates cell proliferation and synthesis of photoprotective eumelanin pigments. Certain MC1R alleles have been associated with increased risk of melanoma. This can be theoretically considered on two grounds. First, gain-of-function mutations may stimulate proliferation, thus promoting dysplastic lesions. Second, and opposite, loss-of-function mutations may decrease eumelanin contents, and impair protection against the carcinogenic effects of UV light, thus predisposing to skin cancers. To test these possibilities, we sequenced the MC1R gene from seven human melanoma cell (HMC) lines and three giant congenital nevus cell (GCNC) cultures. Four HMC lines and two GCNC cultures contained MC1R allelic variants. These were the known loss-of-function Arg142His and Arg151Cys alleles and a new variant, Leu93Arg. Moreover, impaired response to a superpotent ,MSH analog was demonstrated for the cell line carrying the Leu93Arg allele and for a HMC line homozygous for wild-type MC1R. Functional analysis in heterologous cells stably or transiently expressing this variant demonstrated that Leu93Arg is a loss-of-function mutation abolishing agonist binding. These results, together with site-directed mutagenesis of the vicinal Glu94, demonstrate that the MC1R second transmembrane fragment is critical for agonist binding and maintenance of a resting conformation, whereas the second intracellular loop is essential for coupling to the cAMP system. Therefore, loss-of-function, but not activating MC1R mutations are common in HMC. Their study provides important clues to understand MC1R structure-function relationships. [source] Tissue granuloma structure-function in experimental visceral leishmaniasisINTERNATIONAL JOURNAL OF EXPERIMENTAL PATHOLOGY, Issue 5 2001Henry W. Murray In experimental visceral leishmaniasis in normal mice (BALB/c, C57BL/6) acquired resistance to Leishmania donovani, a protozoan which targets tissue macrophages, depends upon T cells, Th1 cell-type cytokine generation and activated mononuclear phagocytes. In the intact host, initial control and eventual resolution of L. donovani hepatic infection in normal mice is expressed by and accomplished within well-formed, mature tissue granulomas. In the liver, these immunologically active, inflammatory structures are assembled around a core of fused, parasitized resident macrophages (Kupffer cells) which come to be encircled by both cytokine-secreting T cells and influxing leishmanicidal blood monocytes. This pro-host defense granuloma structure-function relationship, in which histologically mature granulomas provide the microenvironment for intracellular L. donovani killing, however, is only one of seven which have been identified through experimental modifications in this model. This report reviews these structure-function relationships and illustrates the broad spectrum of additional possible responses. These responses range from structurally intact granulomas which provide no antileishmanial function (the ,ineffective' granuloma), to enlarged granulomas which show enhanced parasite killing (the ,hypertrophied' granuloma), to effective antileishmanial activity in the absence of any tissue reaction (the ,invisible' granuloma). [source] Formation and applications of stable 10 nm to 500 nm supramolecular porphyrinic materialsISRAEL JOURNAL OF CHEMISTRY, Issue 3 2005Charles Michael Drain Nanoscaled materials of organic dyes are of interest for a variety of potential applications because of the rich photonic properties that this class of molecules can impart. One mode to form such nanoscaled materials is via self-organization and self-assembly, using reasonably well understood methods in supramolecular chemistry. But there are inherent complexities that arise from the use of organic-based supramolecular materials, including stability toward dioxygen, structural stability, and nanoarchitectures that may change with environmental conditions. Porphyrinoids have rich photonic properties yet are remarkably stable, have a rigid core, are readily functionalized, and metalation of the macrocycle can impart a plethora of optical, electronic, and magnetic properties. While there are many <10 nm porphyrinic assemblies, which may or may not self-organize into crystals, there is a paucity of 10,500 nm porphyrinic materials that can be isolated and stored. A variety of strategies towards the latter nanoscopic porphyrinic materials are discussed in terms of design, construction, and nanoarchitecture. The hierarchical structures include colloids, nanorods, nanotubes, nanorings, and nano-crystalline materials. This prolegomenon emphasizes the supramolecular chemistry, structure-stability, and structure-function relationships. The goal herein is to examine general trends and delineate general principles. [source] Hemoprotein time-resolved X-ray crystallographyIUBMB LIFE, Issue 3 2008Mario Milani Abstract In the last decade the role of structural dynamics in controlling protein function was actively investigated using new and advanced experimental approaches. In particular, time resolved crystallography, despite some practical difficulties, is being used extensively to complement the study of protein structure-function relationships with information on the dynamics, based on experimental evidence. Here we present a short overview of the results obtained on dynamical properties of myoglobin and homologous hemoproteins, where the photosensitive heme-Fe,ligand bond has allowed transient intermediates to be studied by different flash photolysis methods coupled to Laue X-ray diffraction, thus highlighting some of the dynamical events that characterize diffusion of a diatomic ligand to/from the heme in model hemoproteins. © 2008 IUBMB IUBMB Life, 60(3): 154,158, 2008 [source] Decorin antisense gene therapy improves functional healing of early rabbit ligament scar with enhanced collagen fibrillogenesis in vivoJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2000Norimasa Nakamura Injured ligaments heal with scar tissue, which has mechanical properties inferior to those of normal ligament, potentially resulting in re-injury, joint instability, and subsequent degenerative arthritis. In ligament scars, normal large-diameter collagen fibrils have been shown to be replaced by a homogenous population of small collagen fibrils. Because collagen is a major tensile load-bearing matrix element and because the proteoglycan decorin is known to inhibit collagen fibrillogenesis, we hypothesized that the restoration of larger collagen fibrils in a rabbit ligament scar, by down-regulating the proteoglycan decorin, would improve the mechanical properties of scar. In contrast to sense and injection-treated controls, in vivo treatment of injured ligament by antisense decorin oligodeoxynucleotides led to an increased development of larger collagen fibrils in early scar and a significant improvement in both scar failure strength (83,85% improvement at 6 weeks; p < 0.01) and scar creep elongation (33,48% less irrecoverable creep; p < 0.03) under loading. This is the first report that in vivo manipulation of collagen fibrillogenesis improves tissue function during repair processes with gene therapy. These findings not only suggest the potential use of this type of approach to improve the healing of various soft tissues (skin, ligament, tendon, and so on) but also support the use of such methods to better understand specific structure-function relationships in scars. [source] Structure, function, and regulation of renal organic anion transportersMEDICINAL RESEARCH REVIEWS, Issue 6 2002Guofeng You Abstract Renal elimination of anionic drugs, xenobiotics, and toxins is necessary for the survival of mammalian species. This process is mediated by vectorial transport from blood to urine through the cooperative functions of specific transporters in the basolateral and apical membranes of the proximal tubule epithelium. The first step of this process is the extraction of organic anions from the peritubular blood plasma into proximal tubule cells largely through the organic anion transporter (OAT) pathway. Therefore, the OAT pathway is one of the major sites for body drug clearance/detoxification. As a result, it is also the site for drug,drug interaction and drug-induced nephrotoxicity. To maximize therapeutic efficacy and minimize toxicity, the structure-function relationships of OATs and their regulation must be defined. The recent cloning and identification of OATs have paved the way for such investigations. This review summarizes the available data on the general properties of OATs, focusing in particular on the recent progress made from the author's laboratory as well as from other's, on the molecular characterization of the structure-function relationships of OATs and their regulatory mechanisms. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 6, 602,616, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10019 [source] Recent advances in rational gene transfer vector design based on poly(ethylene imine) and its derivativesTHE JOURNAL OF GENE MEDICINE, Issue 8 2005Michael Neu Abstract The continually increasing wealth of knowledge about the role of genes involved in acquired or hereditary diseases renders the delivery of regulatory genes or nucleic acids into affected cells a potentially promising strategy. Apart from viral vectors, non-viral gene delivery systems have recently received increasing interest, due to safety concerns associated with insertional mutagenesis of retro-viral vectors. Especially cationic polymers may be particularly attractive for the delivery of nucleic acids, since they allow a vast synthetic modification of their structure enabling the investigation of structure-function relationships. Successful clinical application of synthetic polycations for gene delivery will depend primarily on three factors, namely (1) an enhancement of the transfection efficiency, (2) a reduction in toxicity and (3) an ability of the vectors to overcome numerous biological barriers after systemic or local administration. Among the polycations presently used for gene delivery, poly(ethylene imine), PEI, takes a prominent position, due to its potential for endosomal escape. PEI as well as derivatives of PEI currently under investigation for DNA and RNA delivery will be discussed. This review focuses on structure-function relationships and the physicochemical aspects of polyplexes which influence basic characteristics, such as complex formation, stability or in vitro cytotoxicity, to provide a basis for their application under in vivo conditions. Rational design of optimized polycations is an objective for further research and may provide the basis for a successful cationic polymer-based gene delivery system in the future. Copyright © 2005 John Wiley & Sons, Ltd. [source] Computer programming and biomolecular structure studies: A step beyond internet bioinformaticsBIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION, Issue 1 2006Vladimir A. Liki Abstract This article describes the experience of teaching structural bioinformatics to third year undergraduate students in a subject titled Biomolecular Structure and Bioinformatics. Students were introduced to computer programming and used this knowledge in a practical application as an alternative to the well established Internet bioinformatics approach that relies on access to the Internet and biological databases. This was an ambitious approach considering that the students mostly had a biological background. There were also time constraints of eight lectures in total and two accompanying practical sessions. The main challenge was that students had to be introduced to computer programming from a beginner level and in a short time provided with enough knowledge to independently solve a simple bioinformatics problem. This was accomplished with a problem directly relevant to the rest of the subject, concerned with the structure-function relationships and experimental techniques for the determination of macromolecular structure. [source] Binding modules alter the activity of chimeric cellulases: Effects of biomass pretreatment and enzyme source,BIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Tae-Wan Kim Abstract Improving the catalytic activity of cellulases requires screening variants against solid substrates. Expressing cellulases in microbial hosts is time-consuming, can be cellulase specific, and often leads to inactive forms and/or low yields. These limitations have been obstacles for improving cellulases in a high-throughput manner. We have developed a cell-free expression system and used it to express 54 chimeric bacterial and archaeal endoglucanases (EGs), with and without cellulose binding modules (CBMs) at either the N- or C-terminus, in active enzyme yields of 100,350,µg/mL. The platform was employed to systematically study the role of CBMs in cellulose hydrolysis toward a variety of natural and pretreated solid substrates, including ionic-liquid pretreated Miscanthus and AFEX-pretreated corn stover. Adding a CBM generally increased activity against crystalline Avicel, whereas for pretreated substrates the effect of CBM addition depended on the source of cellulase. The cell-free expression platform can thus provide insights into cellulase structure-function relationships for any substrate, and constitutes a powerful discovery tool for evaluating or engineering cellulolytic enzymes for biofuels production. Biotechnol. Bioeng. 2010;107:601,611. © 2010 Wiley Periodicals, Inc. [source] | |||||||||||||