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Jay R. Knutson

Other affiliations: GlaxoSmithKline, University of Iowa, Georgetown University  ...read more
Bio: Jay R. Knutson is an academic researcher from National Institutes of Health. The author has contributed to research in topics: Quenching (fluorescence) & Fluorescence-lifetime imaging microscopy. The author has an hindex of 35, co-authored 103 publications receiving 4412 citations. Previous affiliations of Jay R. Knutson include GlaxoSmithKline & University of Iowa.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a procedure for simultaneous analysis of multiple fluorescence decay curves is described, which exploits relationships between individual decays, and results in increased model testing sensitivity and more accurate parameter recovery.

565 citations

Journal ArticleDOI
TL;DR: It was concluded that dimerization can account for only part of the quenching of 5(6)-carboxyfluorescein, and no direct evidence for collisional self-quenched of 6CF could be found, although a model compound, salicylate, did quench weakly.

366 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the individual fluorescence spectra of two or more components in a mixture can be extracted without prior knowledge of their spectral shapes or degree of overlap.
Abstract: A procedure is described for using nanosecond time resolved fluorescence decay data to obtain decay-associated fluorescence spectra. It is demonstrated that the individual fluorescence spectra of two or more components in a mixture can be extracted without prior knowledge of their spectral shapes or degree of overlap. The procedure is also of value for eliminating scattered light artifacts in the fluorescence spectra of turbid samples. The method was used to separate the overlapping emission spectra of the two tryptophan residues in horse liver alcohol dehydrogenase. Formation of a ternary complex between the enzyme, NAD+, and pyrazole leads to a decrease in the total tryptophan fluorescence. It is shown that the emission of both tryptophan residues decreases. The buried tryptophan (residue 314) undergoes dynamic quenching with no change in the spectral distribution. Under the same conditions, the fluorescence intensity of tryptophan (residue 15) decreases without a change in decay time but with a red shift of the emission spectrum. There is also a decrease in tryptophan fluorescence intensity when the free enzyme is acid denatured (succinate buffer, pH 4.1). The denatured enzyme retains sufficient structure to provide different microenvironments for different tryptophan residues as reflected by biexponential decay and spectrally shifted emission spectra (revealed by decay association). The value of this technique for studies of microheterogeneity in biological macromolecules is discussed.

197 citations

Journal ArticleDOI
TL;DR: This new class of fluorophore yields promising probes for the study of protein/DNA interactions that are suitable for synthesis as phosphormidites and site-specific incorporation into oligonucleotides.

174 citations

Journal ArticleDOI
TL;DR: Results suggest that Zn2+ promotes a conformation with enhanced oligomerization and thereby stimulates Mg(2+)-dependent 3'-processing and may imply that multimers larger than dimers (tetramers and possibly octamers) are required for in vitro activity of integrase in the presence of Zn 2+ and Mg2+.
Abstract: It has been recently demonstrated that the Mg2+-dependent 3‘-processing activity of purified human immunodeficiency virus type-1 (HIV-1) integrase is stimulated by the addition of exogenous Zn2+ [Lee, S. P., & Han, M. K. (1996) Biochemistry 35, 3837−3844]. This activation was hypothesized to result from integrase self-association. In this report, we examine the Zn2+ content of purified HIV-1 integrase by atomic absorption spectroscopy and by application of a thiol modification reagent, p-(hydroxymercuri)benzenesulfonate, with a metallochromic indicator, 4-(2-pyridylazo)resorcinol. We find that the Zn2+ content of HIV-1 integrase varies from 0.1 to 0.92 equiv of Zn2+ per monomer depending on the conditions of protein purification. In vitro activity assays, time-resolved fluorescence emission anisotropy, and gel filtration chromatographic analyses all indicate that EDTA yields an apoprotein which is predominantly monomeric and less active with Mg2+. Further, sedimentation equilibrium studies reveal that rec...

173 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: Of considerable interest is the recent discovery that some chemokines function as HIV-suppressive factors by interacting with chemokine receptors which, together with CD4, were recognized as the binding sites for HIV-1.
Abstract: Interleukin 8, the first chemokine to be characterized, was discovered nearly ten years ago. Today, more than 30 human chemokines are known. They are often upregulated in inflammation and act mainly on leukocytes inducing migration and release responses. The present review deals largely with the new developments of the last three years. Several structural studies have shown that most chemokines form dimers. The dimers, however, dissociate upon dilution, and the monomers constitute the biologically active form. Chemokine activities are mediated by seven-transmembrane-domain, G protein coupled receptors, five of which were discovered in the past three years. The primary receptor-binding domain of all chemokines is near the NH2 terminus, and antagonists can be obtained by truncation or substitutions in this region. Major progress has been made in the understanding of chemokine actions on T lymphocytes that respond to several CC chemokines but also to IP10 and Mig, two CXC chemokines that selectively attract ...

2,249 citations

Journal ArticleDOI
TL;DR: A practical guide to using smFRET, focusing on the study of immobilized molecules that allow measurements of single-molecule reaction trajectories from 1 ms to many minutes, is provided.
Abstract: Single-molecule fluorescence resonance energy transfer (smFRET) is one of the most general and adaptable single-molecule techniques. Despite the explosive growth in the application of smFRET to answer biological questions in the last decade, the technique has been practiced mostly by biophysicists. We provide a practical guide to using smFRET, focusing on the study of immobilized molecules that allow measurements of single-molecule reaction trajectories from 1 ms to many minutes. We discuss issues a biologist must consider to conduct successful smFRET experiments, including experimental design, sample preparation, single-molecule detection and data analysis. We also describe how a smFRET-capable instrument can be built at a reasonable cost with off-the-shelf components and operated reliably using well-established protocols and freely available software.

1,929 citations

Journal ArticleDOI
TL;DR: The lifetime of a photophysical process is the time required by a population of N electronically excited molecules to be reduced by a factor of e via the loss of energy through fluorescence and other non-radiative processes and the average length of time τ is called the mean lifetime, or simply lifetime.
Abstract: When a molecule absorbs a photon of appropriate energy, a chain of photophysical events ensues, such as internal conversion or vibrational relaxation (loss of energy in the absence of light emission), fluorescence, intersystem crossing (from singlet state to a triplet state) and phosphorescence, as shown in the Jablonski diagram for organic molecules (Fig. 1). Each of the processes occurs with a certain probability, characterized by decay rate constants (k). It can be shown that the average length of time τ for the set of molecules to decay from one state to another is reciprocally proportional to the rate of decay: τ = 1/k. This average length of time is called the mean lifetime, or simply lifetime. It can also be shown that the lifetime of a photophysical process is the time required by a population of N electronically excited molecules to be reduced by a factor of e. Correspondingly, the fluorescence lifetime is the time required by a population of excited fluorophores to decrease exponentially to N/e via the loss of energy through fluorescence and other non-radiative processes. The lifetime of photophycal processes vary significantly from tens of femotoseconds for internal conversion1,2 to nanoseconds for fluorescence and microseconds or seconds for phosphorescence.1 Open in a separate window Figure 1 Jablonski diagram and a timescale of photophysical processes for organic molecules.

1,829 citations

Journal ArticleDOI
TL;DR: The methodology for global and target analysis of time-resolved spectra is reviewed and the combination of a model for the kinetics and for the spectra of the components results in a more powerful spectrotemporal model.

1,388 citations