Optical switching of dipolar interactions on proteins (original) (raw)
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Family of site-selective molecular optical switches
2005
We describe the design, synthesis, and characterization of a family of thiol-reactive optical switches for labeling proteins and other biomolecules. Site-selective introduction of photochromic probes within biomolecules is being used as part of a new approach for optical control of biomolecular interactions and activities within cells. The thiol-reactive photochromic probes described in this report include a spironaphthoxazine and five spirobenzopyrans. The location of the thiol-reactive group on the spirobenzopyran is different for each probe; this feature can be used to control the geometry of the optical switch within a bioconjugate. The photochromes undergo rapid and reversible, optically driven transitions between a colorless spiro (SP) state and a brightly colored merocyanine (MC) state. The MC absorption of a spironaphthoxazine conjugate is red shifted by more than 100 nm compared to the equivalent spirobenzopyran, which may be exploited for the independent control of the MC to SP transition for up to two different spironaphthoxazine and spirobenzopyran conjugates within the same sample.
Theoretical Chemistry Accounts, 2007
In recent years, computational photochemistry has become a valid tool for the investigation of photophysical properties and photochemical reaction mechanisms in organic chromophores. Theoretical chemists can now adapt their tools to the subject under investigation and to the type and accuracy of the desired information. Different computational strategies can now be adopted to characterize different aspects of the photoinduced molecular reactivity of a given chromophore and to provide, in principle, a quite detailed description of the reactive process from energy absorption to photoproducts formation. A basic aim is to establish a correlation between the structure of the molecule and its photochemical outcome, and, in particular, to assess the effect of modifications of the chromophore and of the molecular environment. In this perspective recent advances and applications of photoinduced cis trans isomerizations involving some organic chromophores active in biologically or technologically relevant problems is reviewed here and discussed in the light of new results. In particular, the photochemistry of azobenzene, retinals and of the green fluorescent protein chromophore is considered, taking into account structural changes and environment effects. The results presented in this work are intended to be a first step toward the design of chromophores that can act as molecular photoswitches.
Biophysical Journal, 1995
Gln-41 on G-actin was specifically labeled with a fluorescent probe, dansyl ethylenediamine (DED), via transglutaminase reaction to explore the conformational changes in subdomain 2 of actin. Replacement of Ca2+ with Mg2+ and ATP with ADP on G-actin produced large changes in the emission properties of DED. These substitutions resulted in blue shifts in the wavelength of maximum emission and increases in DED fluorescence. Excitation of labeled actin at 295 nm revealed energy transfer from tryptophans to DED. Structure considerations and Cu2' quenching experiments suggested that Trp-79 and/or Trp-86 serves as energy donors to DED. Energy transfer from these residues to DED on Gln-41 increased with the replacement of Ca2+ with Mg2+ and ATP with ADP. Polymerization of Mg-G-actin with MgCI2 resulted in much smaller changes in DED fluorescence than divalent cation substitution. This suggests that the conformation of loop 38-52 on actin is primed for the polymerization reaction by the substitution of Ca2+ with Mg2+ on G-actin.
Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1985
Fluorescence energy transfers were studied in order to investigate the spatial relationships between the nucleotide-binding site, the metal-binding site and the Cys-373 residue in the G-actin molecule. When l-N6-ethenoadenosine-5'-triphosphate (e-AT]P) in the nucleotide-binding site and Co 2+ or Ni 2+ in the metal-binding site were used as fluorescence donor and acceptor, respectively, the fluorescence intensity of e-ATP was perfectly quenched by Ni 2+ or Co 2+. This indicated that the nncleotide-hinding site is very close to the metal-binding site; the distance should he less than 10 k,. When N-iodoacetyl-N'-(5-suifo-lnaphthyl)ethylenediamine (IAEDANS) bound to Cys-373 resklue ami Co 2+ in the metal-binding site were used as a fluorescence donor and an acceptor, respectively, the transfer efficiency was equal to 5 +_ 1%. The corresponding distance was calculated to he 23-32 k,, assuming a random orientation factor K 2 --2//3.
Molecules, 2012
Photoswitchable spiropyran has been conjugated to the crowned ring system DO3A, which improves its solubility in dipolar and polar media and stabilizes the merocyanine isomer. Adding the lanthanide ion gadolinium(III) to the macrocyclic ring system leads to a photoresponsive magnetic resonance imaging contrast agent that displays an increased spin-lattice relaxation time (T 1 ) upon visible light stimulation. In this work, the photoresponse of this photochromic molecule to weak light illumination using blue and green light emitting diodes was investigated, simulating the emission spectra from bioluminescent enzymes. Photon emission rate of the light emitting diodes was changed, from 1.75 × 10 16 photons·s −1 to 2.37 × 10 12 photons·s −1 . We observed a consistent visible light-induced isomerization of the merocyanine to the spiropyran form with photon fluxes as low as 2.37 × 10 12 photons·s −1 resulting in a relaxivity change of the compound. This demonstrates the potential for use of the described imaging probes in low light level applications such as sensing bioluminescence enzyme activity. The isomerization behavior of gadolinium(III)-ion complexed and non-complexed spiropyran-DO3A was analyzed in water and ethanol solution in response to low light illumination and compared to the emitted photon emission rate from over-expressed Gaussia princeps luciferase.
The Journal of Physical Chemistry B, 2011
The present work describes the interaction of a promising cancer cell photosensitizer, harmane (HM), with a model transport protein, Bovine Serum Albumin (BSA). The studied molecule of interest (HM) belongs to the family of naturally occurring fluorescent drug-binding alkaloids, the β-carbolines. A combined use of steady-state and time-resolved fluorescence techniques is applied to follow and characterize the binding interaction. The polarity-dependent prototropic activity of HM is found to be responsible for the commendable sensitivity of the probe to the protein environments and is distinctly reflected on the emission profile. Steady-state fluorescence anisotropy study reveals the impartation of a considerable degree of motional restriction on the drug molecule as a result of binding to the protein. Contrary to the single-exponential nature of fluorescence anisotropy decay of HM in aqueous buffer, they are found to be biexponential in the protein environment. The rotational relaxation dynamics of HM within the protein has been interpreted on the lexicon of the Two-Step and Wobbling-in-Cone model. The probable binding location for the cationic drug is found to be the hydrophilic binding zone of BSA, i.e., domain I (characterized by a net negative charge). The AutoDock-based blind docking simulation has been explored for evaluating an unbiased result of the probable interaction site of HM in the protein. To unfold the effect of binding of the drug on the secondary structural content of the protein, circular dichroism (CD) spectroscopy has been exploited to see that binding of the drug accompanies some decrease in R-helical content of BSA, and the effect gradually saturates toward a higher drug/protein molar ratio.
Integrated optical investigation of two light-sensitive proteins
2017
Integrated optics is one of the most intensively investigated fields when working on alternative methods to overcome the disadvantages of integrated electronics. Besides inorganic active optical crystals, dyes and polymers, molecules of biological origin with suitable nonlinear optical properties can also find applications in integrated opticalbiophotonic-devices. The state-of-the-art photonic integration technology is ready to provide the passive elements of integrated optical circuits. The bottleneck in integrated optics is to find a proper nonlinear optical material that is supposed to be the cladding medium in waveguide-based photonic applications, performing light-controlled active functions. Based on our earlier results, here we present the experimental demonstration of subpicosecond photonic switching with an alternative approach, where the active role is performed by a biological material, the chromoprotein bacteriorhodopsin. Moreover, measurements of the light-induced refractive index change performed on a dried film of the Photoactive Yellow Protein are also presented. Our findings show that these photochromic pigments can be promising candidates as active nonlinear optical materials for all-optical data processing in future biophotonic applications. These results may serve as a basis for the future realization of protein-based integrated optical devices that can eventually lead to a conceptual revolution in the development of telecommunication technologies.
Biophysical Journal, 1997
Temperature dependence of the fluorescence intensity and anisotropy decay of N-(iodoacetyl)-N'-(5-sulfo-1naphthyl)ethylenediamine attached to Cys374 of actin monomer was investigated to characterize conformational differences between Caand Mg-G-actin. The fluorescence lifetime is longer in Mg-G-actin than that in Ca-G-actin in the temperature range of 5-34oC. The width of the lifetime distribution is smaller by 30% in Mg-saturated actin monomer at 50C, and the difference becomes negligible above 300C. The semiangle of the cone within which the fluorophore can rotate is larger in Ca-G-actin at all temperatures. Electron paramagnetic resonance measurements on maleimide spin-labeled (on Cys374) monomer actin gave evidence that exchange of Ca2+ for Mg2+ induced a rapid decrease in the mobility of the label immediately after the addition of Mg2+. These results suggest that the C-terminal region of the monomer becomes more rigid as a result of the replacement of Ca2+ by Mg2+. The change can be related to the difference between the polymerization abilities of the two forms of G-actin.
Journal of Biological Chemistry, 1999
The temperature profile of the fluorescence resonance energy transfer efficiency normalized by the fluorescence quantum yield of the donor in the presence of acceptor, f, was measured in a way allowing the independent investigation of (i) the strength of interaction between the adjacent protomers (intermonomer flexibility) and (ii) the flexibility of the protein matrix within actin protomers (intramonomer flexibility). In both cases the relative increase as a function of temperature in f is larger in calcium-F-actin than in magnesium-Factin in the range of 5-40°C, which indicates that both the intramonomer and the intermonomer flexibility of the actin filaments are larger in calcium-F-actin than those in magnesium-F-actin. The intermonomer flexibility was proved to be larger than the intramonomer one in both the calcium-F-actin and the magnesium-F-actin. The distance between Gln 41 and Cys 374 residues was found to be cation-independent and did not change during polymerization at 21°C. The steady-state fluorescence anisotropy data of fluorophores attached to the Gln 41 or Cys 374 residues suggest that the microenvironments around these regions are more rigid in the magnesiumloaded actin filament than in the calcium-loaded form.