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41.
42.
Previous investigations have shown that bovine growth hormone (bGH, somatotropin) unfolds through a reversible multistate process with at least one stable equilibrium intermediate. In extending our knowledge of the folding process for bGH, we demonstrate that a self-associated form of partially denatured bGH is formed during equilibrium unfolding experiments. The self-associated species has been identified by hydrodynamic measurements (size exclusion high-performance liquid chromatography and static and dynamic light scattering) and by measurements of the bGH concentration dependence of aromatic amino acid spectral properties (fluorescence, second-derivative absorption, and circular dichroism). The apparent maximum concentration for self-association occurs when bGH is partially denatured, i.e., at 3.7 M guanidine hydrochloride or 8.5 M urea, and its formation is reversible. Some of the properties of the self-associated species include quenched tryptophan fluorescence, increased tryptophan circular dichroism intensity at 300 nm, polar tryptophan environment, and a weight-average radius of about 5 nm. The self-association of bGH is mediated by specific intermolecular interactions with little increase in molecular size occurring above the saturation level of 4 mg/mL bGH. These phenomena have important implications for the design and interpretation of folding experiments in vitro and may have physiological consequences. 相似文献
43.
Antigen/antibody complexes can efficiently target antigen presenting cells to allow stimulation of the cellular immune response. Due to the difficulty of manufacture and their inherent instability complexes have proved inefficient cancer vaccines. However, anti-idiotypic antibodies mimicking antigens have been shown to stimulate both antibody and T cell responses. The latter are due to T cell mimotopes expressed within the complementarity-determining regions (CDRs) of antibodies that are efficiently presented to dendritic cells in vivo. Based on this observation we have designed a DNA vaccine platform called ImmunoBody™, where cytotoxic T lymphocyte (CTL) and helper T cell epitopes replace CDR regions within the framework of a human IgG1 antibody. The ImmunoBody™ expression system has a number of design features which allow for rapid production of a wide range of vaccines. The CDR regions of the heavy and light chain have been engineered to contain unique restriction endonuclease sites, which can be easily opened, and oligonucleotides encoding the T cell epitopes inserted. The variable and constant regions of the ImmunoBody™ are also flanked by restriction sites, which permit easy exchange of other IgG subtypes. Here we show a range of T cell epitopes can be inserted into the ImmunoBody™ vector and upon immunization these T cell epitopes are efficiently processed and presented to stimulate high frequency helper and CTL responses capable of anti-tumor activity.Key words: DNA vaccines, cancer vaccines, melanoma, CTL, helper T cells 相似文献
44.
45.
Receptor cells of the vomeronasal organ (VNO) are thought to detect
pheromone-like molecules important for reproductive physiology. Several
compounds derived from male mouse urine have been demonstrated to affect
endocrine events in female mice. In the present study, the ability of these
compounds to affect VNO activity was tested. In dissociated VNO cells held
under voltage clamp conditions, application of dehydro-exo-brevicomin (DHB)
evoked an outward current at negative holding potentials and an inward
current at positive holding potentials. Under current clamp, DHB reduced
action potential firing. Since DHB application caused a decrease in
membrane conductance, this compound appeared to act by reducing inward
current through closing an ion channel. Biochemical experiments tested the
effects of DHB and 2- (sec-butyl)-4,5-dihydrothiazole (SBT) on cAMP levels
in the VNO. A mixture of DHB and SBT decreased cAMP levels in VNO sensory
tissue and had no effect on VNO non-sensory tissue. The results suggest
that pheromones have an inhibitory influence on action potential generation
and on cAMP levels in receptor cells of the VNO.
相似文献
46.
Guo BZ Zhang ZJ Butrón A Widstrom NW Snook ME Lynch RE Plaisted D 《Journal of economic entomology》2004,97(6):2117-2126
In the United States, insecticide is used extensively in the production of sweet corn due to consumer demand for zero damage to ears and to a sweet corn genetic base with little or no resistance to ear-feeding insects. Growers in the southern United States depend on scheduled pesticide applications to control ear-feeding insects. In a study of quantitative genetic control over silk maysin, AM-maysin (apimaysin and methoxymaysin), and chlorogenic acid contents in an F2 population derived from GE37 (dent corn, P1A1) and 565 (sh2 sweet corn, p1a1), we demonstrate that the P1 allele from field corn, which was selected against in the development of sweet corn, has a strong epistatic interaction with the a1 allele in sh2 sweet corn. We detected that the p1 gene has significant effects (P < 0.0001) not only on silk maysin concentrations but also on AM-maysin, and chlorogenic acid concentrations. The a1 gene also has significant (P < 0.0005) effects on these silk antibiotic chemicals. Successful selection from the fourth and fifth selfed backcrosses for high-maysin individuals of sweet corn homozygous for the recessive a1 allele (tightly linked to sh2) and the dominant P1 allele has been demonstrated. These selected lines have much higher (2 to 3 times) concentrations of silk maysin and other chemicals (AM-maysin and chlorogenic acid) than the donor parent GE37 and could enhance sweet corn resistance to corn earworm and reduce the number of applications of insecticide required to produce sweet corn. 相似文献
47.
Carbamoylphosphate synthetase (CPS) catalyzes the first committed step in
pyrimidine biosynthesis, arginine biosynthesis, or the urea cycle.
Organisms may contain either one generalized or two specific CPS enzymes,
and these enzymes may be heterodimeric (encoded by linked or unlinked
genes), monomeric, or part of a multifunctional protein. In order to help
elucidate the evolution of CPS, we have performed a comprehensive
phylogenetic analysis using the 21 available complete CPS sequences,
including a sequence from Sulfolobus solfataricus P2 which we report in
this paper. This is the first report of a complete CPS gene sequence from
an archaeon, and sequence analysis suggests that it encodes an enzyme
similar to heterodimeric CPSII. We confirm that internal similarity within
the synthetase domain of CPS is the result of an ancient gene duplication
that preceded the divergence of the Bacteria, Archaea, and Eukarya, and use
this internal duplication in phylogenetic tree construction to root the
tree of life. Our analysis indicates with high confidence that this
archaeal sequence is more closely related to those of Eukarya than to those
of Bacteria. In addition to this ancient duplication which created the
synthetase domain, our phylogenetic analysis reveals a complex history of
further gene duplications, fusions, and other events which have played an
integral part in the evolution of CPS.
相似文献
48.
49.
There is growing concern about mitigation-driven translocations that move animals from anthropogenic threats at donor sites because of their failure rate and lack of application of scientific principles and best practice. We reviewed all known lizard translocations in New Zealand between 1988 and 2013 and identified 85 translocations of 30 lizard taxa to 46 release sites. Most translocations (62%) were motivated by conservation goals for the species or the release site, and one-third were mitigation-driven translocations, typically motivated by habitat loss due to development. Mitigation-driven translocations began in 2003, and since that time have equalled the number of conservation-motivated translocations. Conservation-motivated translocations usually released lizards on islands without mammalian predators, whereas mitigation-driven translocations usually relocated lizards to mainland sites with introduced predators. Long-term monitoring has been sparse and often rudimentary. Eight lizard translocations have recorded population growth, including one mitigation-driven translocation that was into a fenced reserve. Research on commonly used management techniques to mitigate human-related impacts is recommended to establish whether these techniques benefit lizards in the long term. 相似文献
50.
Walter RB; Rolig RL; Kozak KA; McEntire B; Morizot DC; Nairn RS 《Molecular biology and evolution》1993,10(6):1227-1238
Fishes represent the stem vertebrate condition and have maintained several
gene arrangements common to mammalian genomes throughout the 450 Myr of
divergence from a common ancestor. One such syntenic arrangement includes
the GPI-PEPD enzyme association on Xiphophorus linkage group IV and human
chromosome 19. Previously we assigned the Xiphophorus homologue of the
human ERCC2 gene to linkage group U5 in tight association with the CKM
locus. CKM is also tightly linked to the ERCC2 locus on human chromosome
19, leading to speculation that human chromosome 19 may have arisen by
fusion of two ancestral linkage groups which have been maintained in
fishes. To investigate this hypothesis further, we isolated and sequenced
Xiphophorus fish genomic regions exhibiting considerable sequence
similarity to the human DNA ligase 1 amino acid sequence. Comparison of the
fish DNA ligase sequence with those of other species suggests several modes
of amino acid conservation in this gene. A 2.2-kb restriction fragment
containing part of an X. maculatus DNA ligase 1 exon was used in backcross
hybrid mapping with 12 enzyme or RFLP loci. Significant linkage was
observed between the nucleoside phosphorylase (NP2) and the DNA ligase
(LIG1) loci on Xiphophorus linkage group VI. This assignment suggests that
the association of four DNA repair-related genes on human chromosome 19 may
be the result of chance chromosomal rearrangements.
相似文献