Time-Resolved Fluorescence Spectroscopy is a powerful tool for biochemistry;it can provide unique insights into the structure and assembly of macromolecular complexes. This year, we pursued protein-protein association and ultrafast protein solvation. We also continued studies of DNA using fluorescent nucleotide analogs that reveal disruptions in DNA structures, publishing accounts of analog base pairing effects. We continued and expanded our femtosecond upconversion studies of Trp in proteins and peptides to quantify early """"""""quasistatic self-quenching"""""""" processes. We previously published evidence that extremely rapid (10-100ps) decays are important in several proteins (crystallins, thioredoxin, etc.), as they detect previously silent conformers engaged in ultrafast charge transfer. Our earlier study of protein *solvation* on the 330fs-200ps time scale, using proteins such as Monellin, found QSSQ that others attributed to a class of unique water molecules that desorb from protein in 20ps. Local quenching is the dominant mechanism in all but a few cases we have studied. The QSSQ was found even in simple dipeptides ,suggesting a general process underlies all protein QSSQ. We explored the slow relaxation (50ps) of water in the protein GB1 as a function of pH and temperature, seeking to understand why this one small protein lacks the QSSQ that usually masks relaxation. At the same time,we have been learning the relaxation is nonlocal --i.e., not coupled to local solvent access of Trp (seen in ns lifetimes). We contined collaborative studies with LCE into the status of a primary fuel of heart muscle mitochondria- NADH. Our efforts distinguish free and bound populations of NADH by their different fluorescence lifetimes, and in collaboration with Light Microscopy Core and LCE, we are continually refining 'Decay-Associated Images'software to more rapidly extract profiles of NADH binding within isolated cardiac myocytes. We studied the structural determinants of lifetime for pteridine-based fluorophores that mimic (to the point of base-pairing) the behavior of natural DNA bases, learning which neighbors provide a rigid base """"""""sandwich"""""""" and which permit """"""""flip-out"""""""". We employed the same probes to look at the G-quadruplex formation within DNA (important in teleomeres , division, and regulation). We coupled lifetime and translational diffusion capabilities in time-resolved FCS for this project.

Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
National Heart, Lung, and Blood Institute
Zip Code
Ardeshirpour, Yasaman; Sackett, Dan L; Knutson, Jay R et al. (2018) Using in vivo fluorescence lifetime imaging to detect HER2-positive tumors. EJNMMI Res 8:26
Trachman 3rd, Robert J; Abdolahzadeh, Amir; Andreoni, Alessio et al. (2018) Crystal Structures of the Mango-II RNA Aptamer Reveal Heterogeneous Fluorophore Binding and Guide Engineering of Variants with Improved Selectivity and Brightness. Biochemistry 57:3544-3548
Lucotte, Bertrand M; Powell, Chloe; Knutson, Jay R et al. (2017) Direct visualization of the arterial wall water permeability barrier using CARS microscopy. Proc Natl Acad Sci U S A 114:4805-4810
Rosales, Tilman; Sackett, Dan L; Xu, Jianhua et al. (2015) STAQ: A route toward low power, multicolor nanoscopy. Microsc Res Tech 78:343-55
Xu, Jianhua; Chen, Binbin; Callis, Patrik et al. (2015) Picosecond fluorescence dynamics of tryptophan and 5-fluorotryptophan in monellin: slow water-protein relaxation unmasked. J Phys Chem B 119:4230-9
Biesso, Arianna; Xu, Jianhua; Muíño, Pedro L et al. (2014) Charge invariant protein-water relaxation in GB1 via ultrafast tryptophan fluorescence. J Am Chem Soc 136:2739-47
Dasgeb, Bahar; Smirnov, Aleksandr V; Ardeshirpour, Yasaman et al. (2014) Multiscale BerEp4 molecular imaging of microtumor phantoms: toward theranostics for basal cell carcinoma. Mol Imaging 13:
Biesso, Arianna; Xu, Jianhua; Knutson, Jay R (2014) Upconversion spectrophotofluorometry. Methods Mol Biol 1076:303-19
Combs, Christian A; Smirnov, Aleksandr; Glancy, Brian et al. (2014) Compact non-contact total emission detection for in vivo multiphoton excitation microscopy. J Microsc 253:83-92
Rosales, Tilman; Nie, Zuqin; Kapoor, Varun et al. (2013) Partition of Myc into Immobile vs. Mobile Complexes within Nuclei. Sci Rep 3:1953

Showing the most recent 10 out of 21 publications