Abstract:
:The fluorescence of the supposedly buried tryptophan in ribonuclease T1 has been found to be collisionally quenched by acrylamide with a rate constant of 3 X 10(8) M--1 sec--1. Only a slight decrease in the quenching rate is observed upon a 5-fold increase in the viscosity of the solution. For this to be the case, the diffusion of the quencher must be limited by the protein matrix. To explain the process of diffusion through this complex material, the formation of "holes" in the lattice of a protein due to nanosecond fluctuations must be invoked. Thus, the dynamic character of a protein molecule is revealed. The quenching rate constant has an activation energy of 9 kcal/mol which can be used to characterize the nature of the cohesive forces in the microenvironment about the indole ring. The mechanical properties of a portion of a protein matrix can, therefore, be described as one would for a fluid.
journal_name
Proc Natl Acad Sci U S Aauthors
Eftink MR,Ghiron CAdoi
10.1073/pnas.72.9.3290subject
Has Abstractpub_date
1975-09-01 00:00:00pages
3290-4issue
9eissn
0027-8424issn
1091-6490journal_volume
72pub_type
杂志文章abstract::Newly emerging plants provide the best forage for herbivores. To exploit this fleeting resource, migrating herbivores align their movements to surf the wave of spring green-up. With new technology to track migrating animals, the Green Wave Hypothesis has steadily gained empirical support across a diversity of migrator...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1913783116
更新日期:2019-12-17 00:00:00
abstract::Biodiversity responses to ongoing climate and atmospheric changes will affect both ecosystem processes and the delivery of ecosystem goods and services. Combined effects of co-occurring global changes on diversity, however, are poorly understood. We examined plant diversity responses in a California annual grassland t...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0932734100
更新日期:2003-06-24 00:00:00
abstract::Movement over and colonization of surfaces are important survival strategies for bacteria, and many find it advantageous to perform these activities as a group, using quorum sensing to sample population size and synchronize behavior. It is puzzling however, that swarming-proficient and virulent strains of Vibrio parah...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1113790108
更新日期:2011-11-01 00:00:00
abstract::Multiple paleoclimate proxies are required for robust assessment of past hydroclimatic conditions. Currently, estimates of drought variability over the past several thousand years are based largely on tree-ring records. We produced a 1,500-y record of winter precipitation in the Pacific Northwest using a physical mode...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 历史文章,杂志文章
doi:10.1073/pnas.1201083109
更新日期:2012-07-17 00:00:00
abstract::A major protein tyrosine phosphatase (PTPase 1B) has been isolated in essentially homogeneous form from the soluble and particulate fractions of human placenta. Unexpectedly, partial amino acid sequences displayed no homology with the primary structures of the protein Ser/Thr phosphatases deduced from cDNA clones. How...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.19.7182
更新日期:1988-10-01 00:00:00
abstract::The mechanism by which antifreeze proteins (AFPs) irreversibly bind to ice has not yet been resolved. The ice-binding site of an AFP is relatively hydrophobic, but also contains many potential hydrogen bond donors/acceptors. The extent to which hydrogen bonding and the hydrophobic effect contribute to ice binding has ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1100429108
更新日期:2011-05-03 00:00:00
abstract::The transmission of complexity during DNA replication has been investigated to clarify the significance of this molecular property in a deterministic process. Complexity was equated with the amount of randomness within an ordered molecular structure and measured by the entropy of a posteriori probabilities for discret...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.76.5.2288
更新日期:1979-05-01 00:00:00
abstract::Methyl groups placed on varphiXsB1 replicative form DNA by the Escherichia coli B modification enzyme are located in the overlap between fragments Mbo II-3 and Alu I-2, a 61-base-pair DNA segment. Mutations that led to loss of susceptibility to restriction by E. coli B occurred within this segment at three positions s...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.75.5.2271
更新日期:1978-05-01 00:00:00
abstract::The Millennium Ecosystem Assessment (MA) introduced a new framework for analyzing social-ecological systems that has had wide influence in the policy and scientific communities. Studies after the MA are taking up new challenges in the basic science needed to assess, project, and manage flows of ecosystem services and ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0808772106
更新日期:2009-02-03 00:00:00
abstract::Phospholipase C-gamma1 (PLC-gamma1) contains two tandem Src homology 2 (SH2) domains. The NH(2)-terminal SH2 domain has been known to mediate the binding of PLC-gamma1 to receptor protein tyrosine kinases, which then activate PLC-gamma1 via phosphorylation at Y783. We now show that the phosphorylated Y783 residue (pY7...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0409590102
更新日期:2005-03-22 00:00:00
abstract::Electronic nematicity, a correlated state that spontaneously breaks rotational symmetry, is observed in several layered quantum materials. In contrast to their liquid-crystal counterparts, the nematic director cannot usually point in an arbitrary direction (XY nematics), but is locked by the crystal to discrete direct...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1909172117
更新日期:2020-03-24 00:00:00
abstract::A vaccinia virus host range mutant (hr mutant) deleted of 18 kilobase pairs at the left end of the genome has been employed to precisely map a viral gene required for multiplication in human cells. DNA fragments from the wild-type virus were inserted into the thymidine kinase gene of mutant virus by means of in vivo h...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.83.15.5573
更新日期:1986-08-01 00:00:00
abstract::It is generally acknowledged that cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4/CD152) plays a pivotal role in the regulation of T-cell activation and the establishment of self-tolerance in the periphery. CTLA-4-deficient (CTLA-4KO) mice develop a lymphoproliferative disorder and die within 4 weeks of birth, sug...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0803186106
更新日期:2009-03-03 00:00:00
abstract::Activation of eukaryotic class II gene expression involves the formation of a transcription initiation complex that includes RNA polymerase II, general transcription factors, and SRB components of the holoenzyme. Negative regulators of transcription have been described, but it is not clear whether any are general repr...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.94.7.3145
更新日期:1997-04-01 00:00:00
abstract::Enhancing immune responses with immune-modulatory monoclonal antibodies directed to inhibitory immune receptors is a promising modality in cancer therapy. Clinical efficacy has been demonstrated with antibodies blocking inhibitory immune checkpoints such as cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) or PD-1/...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1417320112
更新日期:2015-05-12 00:00:00
abstract::The eukaryotic proteasome mediates degradation of polyubiquitinated proteins. Here we report the single-particle cryoelectron microscopy (cryo-EM) structures of the endogenous 26S proteasome from Saccharomyces cerevisiae at 4.6- to 6.3-Å resolution. The fine features of the cryo-EM maps allow modeling of 18 subunits i...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1601561113
更新日期:2016-03-08 00:00:00
abstract::The addition of 10 mM glycine to a physiological saline bathing Ehrlich ascites tumor cells is followed by a slow increase in cell volume that plateaus between 15 and 30 min at a level approximately equal to 17% greater than the control volume; this increase is not observed when glycine is added to cells suspended in ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.85.1.279
更新日期:1988-01-01 00:00:00
abstract::CD28 is a 44-kDa glycoprotein expressed as a homodimer on the surface of a major subset of human T cells. Previous studies have demonstrated that the binding of monoclonal antibodies to the CD28 surface antigen can augment the proliferation of purified human T cells stimulated with suboptimal doses of mitogens or anti...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.86.4.1333
更新日期:1989-02-01 00:00:00
abstract::l-Serine biosynthesis, a crucial metabolic process in most domains of life, is initiated by d-3-phosphoglycerate (d-3-PG) dehydrogenation, a thermodynamically unfavorable reaction catalyzed by d-3-PG dehydrogenase (SerA). d-2-Hydroxyglutarate (d-2-HG) is traditionally viewed as an abnormal metabolite associated with c...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1619034114
更新日期:2017-09-05 00:00:00
abstract::Epstein-Barr virus-induced gene 3 (EBI3) is a widely expressed IL-12p40-related protein that associates as a heterodimer with either IL-12p35 or an IL-12p35 homologue, p28, to create a new cytokine (IL-27). To define the function of EBI3 in vivo, we generated knockout mice in which the ebi3 gene was targeted by homolo...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.252648899
更新日期:2002-12-24 00:00:00
abstract::The mouse skeletal muscle acetylcholine receptor is regulated, at least in part, by transcriptional mechanisms. As a first step toward defining the cis- and trans-acting factors involved in acetylcholine receptor transcriptional regulation, we examined mouse muscle and fibroblast cells for the presence of DNase I-hype...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.83.21.8405
更新日期:1986-11-01 00:00:00
abstract::Long interspersed nuclear elements 1 (L1) are active retrotransposons that reside in many species, including humans and rodents. L1 elements produce an RNA intermediate that is reverse transcribed to DNA and inserted in a new genomic location. We have tagged an active human L1 element (L1(RP)) with a gene encoding enh...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0337627100
更新日期:2003-02-18 00:00:00
abstract::The absorption spectrum of an activesite specific chromophoric acyl enzyme, sturgeon beta-(2-furyl)-acryloyl-glyceraldehyde-3-phosphate dehydrogenase, is reported. This acyl enzyme undergoes all of the catalyzed reactions characteristic of the intermediate of the physiological acyl enzyme, 3-phospho-D-glyceroyl-glycer...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.70.7.2077
更新日期:1973-07-01 00:00:00
abstract::Synthetic radionuclides, such as the transuranic actinides plutonium, americium, and curium, present severe health threats as contaminants, and understanding the scope of the biochemical interactions involved in actinide transport is instrumental in managing human contamination. Here we show that siderocalin, a mammal...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1508902112
更新日期:2015-08-18 00:00:00
abstract::Cryogenic fluorescent light microscopy of flash-frozen cells stands out by artifact-free fixation and very little photobleaching of the fluorophores used. To attain the highest level of resolution, aberration-free immersion objectives with accurately matched immersion media are required, but both do not exist for imag...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1717282115
更新日期:2018-02-06 00:00:00
abstract::Members of the arenavirus family, famous for their hemorrhagic syndromes, cause distinct neurological disorders; however, cellular and molecular targets as well as pathogenesis of peripheral nervous system disorders associated with these viruses are unknown. Using noncytolytic lymphocytic choriomeningitis virus, the p...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.2232366100
更新日期:2003-12-23 00:00:00
abstract::Periodic fluctuations in past biodiversity, speciation, and extinction have been proposed, with extremely long periods ranging from 26 to 62 million years, although forcing mechanisms remain speculative. In contrast, well-understood periodic Milankovitch climate forcing represents a viable driver for macroevolutionary...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.1714342115
更新日期:2018-05-29 00:00:00
abstract::Heparinase I from Flavobacterium heparinum has important uses for elucidating the complex sequence heterogeneity of heparin-like glycosaminoglycans (HLGAGs). Understanding the biological function of HLGAGs has been impaired by the limited methods for analysis of pure or mixed oligosaccharide fragments. Here, we use me...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.95.8.4182
更新日期:1998-04-14 00:00:00
abstract::A protein fraction from B. subtilis infected with phage SP01 (fraction LGG) stimulates the activity of RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase) core from uninfected bacteria. Fraction LGG contains a protein (P-28, molecular weight 28,000) that is labeled after phage infection and ...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.72.6.2366
更新日期:1975-06-01 00:00:00
abstract::Previous work identified the Rap1 GTPase-activating protein Sipa1 as a germ-line-encoded metastasis modifier. The bromodomain protein Brd4 physically interacts with and modulates the enzymatic activity of Sipa1. In vitro analysis of a highly metastatic mouse mammary tumor cell line ectopically expressing Brd4 demonstr...
journal_title:Proceedings of the National Academy of Sciences of the United States of America
pub_type: 杂志文章
doi:10.1073/pnas.0710331105
更新日期:2008-04-29 00:00:00