Articles by Walter G. Gonzalez in JoVE
Submillisecond Conformational Changes in Proteins Resolved by Photothermal Beam Deflection Walter G. Gonzalez1, Jaroslava Miksovska1 1Department of Chemistry and Biochemistry, Florida International University Here we report an application of the photothermal beam deflection technique in combination with a caged calcium compound, DM-nitrophen, to monitor microsecond and millisecond dynamics and energetics of structural changes associated with the calcium association to a neuronal calcium sensor, Downstream Regulatory Element Antagonist Modulator.
Other articles by Walter G. Gonzalez on PubMed
Emission Switching of 4,6-diphenylpyrimidones: Solvent and Solid State Effects The Journal of Physical Chemistry. A. Aug, 2012 | Pubmed ID: 22856457 The photophysics of 1-ethyl-4,6-bis(4-methoxyphenyl)-2(1H)-pyrimidone (1) and 1-ethyl-4,6-bis(4-(dimethylamino)phenyl)-2(1H)-pyrimidone (2) were investigated to determine the mechanisms of emission switching in response to protonation. UV-vis and steady state emission spectroscopy of the protonated and unprotonated forms across a range of solvents reveal the polarity dependence of the vertical excitation energies. Emission lifetimes and quantum yields show the solvent dependency of the excited states. Emission enhancements were observed in polyethylene glycol solutions and in the solid state (both thin film and single crystal), demonstrating the role of intramolecular rotation in thermal relaxation of the excited states. TD-DFT calculations provide insights into the excited state geometries and the role of intramolecular charge transfer. The collected data show that emission of diphenylpyrimidones can be modulated by four factors, including the identity of the electron-donating auxochrome, protonation state, solvent polarity, and viscosity.
Graphene Oxide As a Quencher for Fluorescent Assay of Amino Acids, Peptides, and Proteins ACS Applied Materials & Interfaces. Dec, 2012 | Pubmed ID: 23173615 Understanding the interaction between graphene oxide (GO) and the biomolecules is fundamentally essential, especially for disease- and drug-related peptides and proteins. In this study, GO was found to strongly interact with amino acids (tryptophan and tyrosine), peptides (Alzheimer's disease related amyloid beta 1-40 and type 2 diabetes related human islet amyloid polypeptide), and proteins (drug-related bovine and human serum albumin) by fluorescence quenching, indicating GO was a universal quencher for tryptophan or tyrosine related peptides and proteins. The quenching mechanism between GO and tryptophan (Trp) or tyrosine (Tyr) was determined as mainly static quenching, combined with dynamic quenching (Förster resonance energy transfer). Different quenching efficiency between GO and Trp or Tyr at different pHs indicated the importance of electrostatic interaction during quenching. Hydrophobic interaction also participated in quenching, which was proved by the presence of nonionic amphiphilic copolymer Pluronic F127 (PF127) in GO dispersion. The strong hydrophobic interaction between GO and PF127 efficiently blocked the hydrophobic interaction between GO and Trp or Tyr, lowering the quenching efficiency.
Photophysical Characterization of a Benzo-fused Analogue of Brooker's Merocyanine: Solvent Polarity and PH Effects The Journal of Physical Chemistry. A. Dec, 2012 | Pubmed ID: 23214717 The photophysical properties of 4-[2-(6-hydroxy-2-naphthalenyl)-ethenyl]-1-methyl-pyridinium (HNEP(+)) and its deprotonated form (NEP), a benzofused derivative of Brooker's merocyanine (BM), were investigated through a combined spectroscopic and computational approach. Despite their structural similarities and similar pK(a) values, HNEP(+)/NEP and BMH(+)/BM differ in the extent of charge delocalization in the ground and excited states. NEP exhibits the spectral characteristics of a charge transfer species in solvents in which BM exists in a charge-delocalized quinoid; however, quantum chemical calculations show that the CT absorption of NEP is not necessarily a consequence of the zwitterionic character. HNEP(+) displays larger Stokes shifts than BMH(+), and NEP demonstrates enhanced solvatochromism relative to BM as a consequence of benzofusion.