Learn More
Electron transfer is used as a probe for angstrom-scale structural changes in single protein molecules. In a flavin reductase, the fluorescence of flavin is quenched by a nearby tyrosine residue by means of photo-induced electron transfer. By probing the fluorescence lifetime of the single flavin on a photon-by-photon basis, we were able to observe the(More)
The lysogenic state of bacteriophage lambda is maintained by CI repressor, which negatively regulates two promoters to block lytic gene expression. Expression of CI is itself controlled by positive and negative feedback as CI binds to O(R) to regulate the P(RM) promoter. In addition to direct interactions with operator DNA, CI tetramers bound at O(L) and(More)
We present a method for the analysis of optical single molecule emission data that exhibit discrete intensity jumps. This new method uses a generalized likelihood ratio test that determines the location of an intensity change point based on individual photon arrival times. This test is applied recursively to an entire single molecule intensity trajectory,(More)
The initiation of DNA replication requires the melting of chromosomal origins to provide a template for replisomal polymerases. In bacteria, the DnaA initiator plays a key role in this process, forming a large nucleoprotein complex that opens DNA through a complex and poorly understood mechanism. Using structure-guided mutagenesis, biochemical, and genetic(More)
Many enzymes mold their structures to enclose substrates in their active sites such that conformational remodeling may be required during each catalytic cycle. In adenylate kinase (AK), this involves a large-amplitude rearrangement of the enzyme's lid domain. Using our method of high-resolution single-molecule FRET, we directly followed AK's domain(More)
Nanostructures of colloidal CdSe/ZnS core/shell quantum dots (QDs) surrounded by a discrete number of Au nanoparticles were generated via DNA hybridization and purified by gel electrophoresis. Statistics from TEM analysis showed a high yield of designed structures. The distance between Au particles and QD, the number of Au around the central QD, and the(More)
The local temperature response inside single living cells upon external chemical and physical stimuli was characterized using quantum dots as nano thermometers. The photoluminescence spectral shifts from endocytosed quantum dots were used to map intracellular heat generation in NIH/3T3 cells following Ca(2+) stress and cold shock. The direct observation of(More)
The photoluminescence dynamics of colloidal CdSe/ZnS/streptavidin quantum dots were studied using time-resolved single-molecule spectroscopy. Statistical tests of the photon-counting data suggested that the simple "on/off" discrete state model is inconsistent with experimental results. Instead, a continuous emission state distribution model was found to be(More)
Real-time chemical imaging of bacterial activities can facilitate a comprehensive understanding of the dynamics of biofilm structures and functions. Synchrotron-radiation-based Fourier transform infrared (SR-FTIR) spectromicroscopy can yield high spatial resolution and label-free vibrational signatures of chemical bonds in biomolecules, but the abundance of(More)
The NtrC-like AAA+ ATPases control virulence and other important bacterial activities through delivering mechanical work to σ54-RNA polymerase to activate transcription from σ54-dependent genes. We report the first crystal structure for such an ATPase, NtrC1 of Aquifex aeolicus, in which the catalytic arginine engages the γ-phosphate of ATP. Comparing the(More)