@article {1646,
	title = {The Role of Oxidation of Silver in Bimetallic Gold{\textendash}Silver Nanocages on Electrocatalytic Activity of Nitrogen Reduction Reaction},
	journal = {The Journal of Physical Chemistry C},
	year = {2019},
	chapter = {11422},
	author = {Nazemi, M. and El-Sayed, M.A.}
}
@article {1638,
	title = {Real-Time Tracking of Autophagy Process in Living Cells Using Plasmonically Enhanced Raman Spectroscopy of Fucoidan-Coated Gold Nanoparticles},
	journal = {Journal of Materials Chemistry B},
	year = {2018},
	author = {Jang, H and K. Kang and El-Sayed, M. A.}
}
@article {1583,
	title = {A Real-Time Surface Enhanced Raman Spectroscopy Study of Plasmonic Photothermal Cell Death Using Targeted Gold Nanoparticles},
	journal = {Journal of the American Chemical Society},
	year = {2016},
	author = {Aioub, Mena S and El-Sayed, Mostafa A.}
}
@article {1380,
	title = {Rapid and Efficient Prediction of Optical Extinction Coefficients for Gold Nanospheres and Gold Nanorods},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	number = {45},
	year = {2013},
	note = {Near, Rachel D. Hayden, Steven C. Hunter, Ronald E., Jr. Thackston, Daniel El-Sayed, Mostafa A.},
	month = {Nov},
	pages = {23950-23955},
	isbn = {1932-7447},
	doi = {10.1021/jp4082596},
	author = {Near, R. D. and Hayden, S. C. and Hunter, R. E. and Thackston, D. and El-Sayed, M. A.}
}
@article {1332,
	title = {Real-Time Molecular Imaging throughout the Entire Cell Cycle by Targeted Plasmonic-Enhanced Rayleigh/Raman Spectroscopy},
	journal = {Nano Letters},
	volume = {12},
	number = {10},
	year = {2012},
	note = {Times Cited: 0Kang, Bin Austin, Lauren A. El-Sayed, Mostafa A.},
	month = {Oct},
	pages = {5369-5375},
	abstract = {Due to their strong enhancement of scattered light, plasmonic nanoparticles have been utilized for various biological and medical applications. Here, we describe a new technique, Targeted Plasmonic-Enhanced Single-Cell Rayleigh/Raman Spectroscopy, to monitor the molecular changes of any cell-component, such as the nucleus, during the different phases of its full cell cycle by simultaneously recording its Rayleigh images and Raman vibration spectra in real-time. The analysis of the observed Raman DNA and protein peaks allowed the different phases of the cell cycle to be identified. This technique could be used for disease diagnostics and potentially improve our understanding of the molecular mechanisms of cellular functions such as division, death, signaling, and drug action.},
	isbn = {1530-6984},
	doi = {10.1021/nl3027586},
	author = {Kang, B. and Austin, Lauren and El-Sayed, M. A.}
}
@article {1088,
	title = {Remote Triggered Release of Doxorubicin in Tumors by Synergistic Application of Thermosensitive Liposomes and Gold Nanorods},
	journal = {Acs Nano},
	volume = {5},
	number = {6},
	year = {2011},
	note = {Agarwal, Abhiruchi Mackey, Megan A. El-Sayed, Mostafa A. Bellamkonda, Ravi V.},
	month = {Jun},
	pages = {4919-4926},
	abstract = {Delivery cif chemotherapeutic agents after encapsulation in nanocarriers such as liposomes diminishes side-effects, as PEGylated nanocarrier pharmacokinetics decrease dosing to healthy tissues and accumulate in tumors due to the enhanced permeability and retention effect. Once in the tumor, however, dosing of the chemotherapeutic to tumor cells is limited potentially by the rate of release from the carriers and the size-constrained, poor diffusivity of nanocarriers in tumor interstitium. Here, we report the design and fabrication of a thermosensitive liposomal nanocarder that maintains its encapsulation stability with a high concentration of doxorubicin payload, thereby minimizing "leak" and attendant toxicity. When used synergistically with PEGylated gold nanorods and near-infrared stimulation, remote triggered release of doxorubicin from thermosensitive liposomes was achieved in a mouse tumor model of human glioblastoma (U87), resulting in a. significant increase in efficacy when compared to nontriggered or nonthermosensitive PEGylated liposomes. This enhancement in efficacy is attributed to increase in tumor-site apoptosis, as was evident from noninvasive apoptosis imaging using Annexin-Vivo 750 probe. This strategy afford; remotely triggered control of tumor dosing of nanocarrier-encapsulated doxorubicin without sacrificing the ability to differentially dose drugs to tumors via the enhanced permeation and retention effect.},
	isbn = {1936-0851},
	doi = {10.1021/nn201010q},
	author = {Agarwal, A. and Mackey, M. A. and El-Sayed, Mostafa A and Bellamkonda, R. V.}
}
@article {808,
	title = {A Reexamination of Active and Passive Tumor Targeting by Using Rod-Shaped Gold Nanocrystals and Covalently Conjugated Peptide Ligands},
	journal = {ACS Nano},
	volume = {4},
	year = {2010},
	note = {doi: 10.1021/nn102055s},
	month = {2010},
	pages = {5887 - 5896},
	publisher = {American Chemical Society},
	abstract = {The targeted delivery of nanoparticles to solid tumors is one of the most important and challenging problems in cancer nanomedicine, but the detailed delivery mechanisms and design principles are still not well understood. Here we report quantitative tumor uptake studies for a class of elongated gold nanocrystals (called nanorods) that are covalently conjugated to tumor-targeting peptides. A major advantage in using gold as a ?tracer? is that the accumulated gold in tumors and other organs can be quantitatively determined by elemental mass spectrometry (gold is not a natural element found in animals). Thus, colloidal gold nanorods are stabilized with a layer of polyethylene glycols (PEGs) and are conjugated to three different ligands: (i) a single-chain variable fragment (ScFv) peptide that recognizes the epidermal growth factor receptor (EGFR); (ii) an amino terminal fragment (ATF) peptide that recognizes the urokinase plasminogen activator receptor (uPAR); and (iii) a cyclic RGD peptide that recognizes the av?3 integrin receptor. Quantitative pharmacokinetic and biodistribution data show that these targeting ligands only marginally improve the total gold accumulation in xenograft tumor models in comparison with nontargeted controls, but their use could greatly alter the intracellular and extracellular nanoparticle distributions. When the gold nanorods are administered via intravenous injection, we also find that active molecular targeting of the tumor microenvironments (e.g., fibroblasts, macrophages, and vasculatures) does not significantly influence the tumor nanoparticle uptake. These results suggest that for photothermal cancer therapy, the preferred route of gold nanorod administration is intratumoral injection instead of intravenous injection.The targeted delivery of nanoparticles to solid tumors is one of the most important and challenging problems in cancer nanomedicine, but the detailed delivery mechanisms and design principles are still not well understood. Here we report quantitative tumor uptake studies for a class of elongated gold nanocrystals (called nanorods) that are covalently conjugated to tumor-targeting peptides. A major advantage in using gold as a ?tracer? is that the accumulated gold in tumors and other organs can be quantitatively determined by elemental mass spectrometry (gold is not a natural element found in animals). Thus, colloidal gold nanorods are stabilized with a layer of polyethylene glycols (PEGs) and are conjugated to three different ligands: (i) a single-chain variable fragment (ScFv) peptide that recognizes the epidermal growth factor receptor (EGFR); (ii) an amino terminal fragment (ATF) peptide that recognizes the urokinase plasminogen activator receptor (uPAR); and (iii) a cyclic RGD peptide that recognizes the av?3 integrin receptor. Quantitative pharmacokinetic and biodistribution data show that these targeting ligands only marginally improve the total gold accumulation in xenograft tumor models in comparison with nontargeted controls, but their use could greatly alter the intracellular and extracellular nanoparticle distributions. When the gold nanorods are administered via intravenous injection, we also find that active molecular targeting of the tumor microenvironments (e.g., fibroblasts, macrophages, and vasculatures) does not significantly influence the tumor nanoparticle uptake. These results suggest that for photothermal cancer therapy, the preferred route of gold nanorod administration is intratumoral injection instead of intravenous injection.},
	isbn = {1936-0851},
	url = {http://dx.doi.org/10.1021/nn102055s},
	author = {Huang, Xiaohua and Peng, Xianghong and Wang, Yiqing and Wang, Yuxiang and Shin, Dong M and El-Sayed, Mostafa A and Nie, Shuming}
}
@article {1109,
	title = {Rapid Thermal Tuning of Chromophore Structure in Membrane Protein},
	journal = {Journal of Physical Chemistry B},
	volume = {113},
	number = {13},
	year = {2009},
	note = {Wang, Jianping El-Sayed, Mostafa A.},
	month = {Apr},
	pages = {4184-4186},
	abstract = {We show that the configuration and the optical property of the retinal chromophore in bacteriorhodopsin (bR) can be tuned dynamically from the all-trans configuration to the 13-cis by using a nanosecond laser-induced temperature-jump. The rapid bleach in the visible absorption optical density of retinal has an apparent formation time of ca. 170 ns, whereas the relaxation process finishes within tens of ms. The dynamical transition of retinal from the all-trans to 13-cis species is believed to occur as a result of rapid protein conformational change especially in the vicinity of retinal binding site. Our study reveals the intrinsic dynamical aspect of the retinal chromophore with respect to the protein structure.},
	isbn = {1520-6106},
	doi = {10.1021/jp901560m},
	author = {Wang, Jianping and El-Sayed, Mostafa A}
}
@article {814,
	title = {Reaction of Platinum Nanocatalyst with the Ferricyanide Reactant to Produce Prussian Blue Analogue Complexes},
	journal = {The Journal of Physical Chemistry C},
	volume = {111},
	year = {2007},
	note = {doi: 10.1021/jp709735n},
	month = {2007},
	pages = {17180 - 17183},
	publisher = {American Chemical Society},
	abstract = {The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[PtIIFeIII(CN)6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [PtIVFeII(CN)6] increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given.The field of catalysis with colloidal nanoparticles is in its infancy. The question of whether the catalysis occurs on the surface of the nanoparticle (thus heterogeneous) or homogeneously in solution using a complex made by the nanoparticle is now being debated. Thus, the molecular mechanism of nanocatalysis has not yet been studied in detail. The first step in this effort is to study the molecular mechanism of the reaction of each reactant with the nanoparticle. This letter is an effort in this direction. A great deal of research has used platinum nanoparticles (PtNPs) to catalyze electron-transfer reactions such as that between thiosulfate and hexacyanoferrate III. We monitored this reaction in detail using optical, Raman, and IR spectroscopies. By increasing the reaction time, two sequential dominant species are formed. The first one is found to have spectral signatures of a Prussian blue analogue with a structure of K[PtIIFeIII(CN)6]. With increasing time, the intensity of the spectrum of this complex is found to decrease, whereas a spectrum similar to that of a complex having the structure of [PtIVFeII(CN)6] increased. A mechanism for the formation of these metal-mixed valency Prussian blue analogues is given.},
	isbn = {1932-7447},
	doi = {10.1021/jp709735n},
	url = {http://dx.doi.org/10.1021/jp709735n},
	author = {Mahmoud, M A and El-Sayed, Mostafa A}
}
@article {815,
	title = {Review of some interesting surface plasmon resonance-enhanced properties of noble metal nanoparticles and their applications to biosystems},
	journal = {Plasmonics},
	volume = {2},
	year = {2007},
	pages = {107-118},
	publisher = {Springer},
	abstract = {Noble metal, especially gold (Au) and silver (Ag) nanoparticles exhibit unique and tunable optical properties on account of their surface plasmon resonance (SPR). In this review, we discuss the SPR-enhanced optical properties of noble metal nanoparticles, with an emphasis on the recent advances in the utility of these plasmonic properties in molecular-specific imaging and sensing, photo-diagnostics, and selective photothermal therapy. The strongly enhanced SPR scattering from Au nanoparticles makes them useful as bright optical tags for molecular-specific biological imaging and detection using simple dark-field optical microscopy. On the other hand, the SPR absorption of the nanoparticles has allowed their use in the selective laser photothermal therapy of cancer. We also discuss the sensitivity of the nanoparticle SPR frequency to the local medium dielectric constant, which has been successfully exploited for the optical sensing of chemical and biological analytes. Plasmon coupling between metal nanoparticle pairs is also discussed, which forms the basis for nanoparticle assembly-based biodiagnostics and the plasmon ruler for dynamic measurement of nanoscale distances in biological systems.},
	isbn = {1557-1955},
	doi = {10.1007/s11468-007-9031-1},
	url = {http://dx.doi.org/10.1007/s11468-007-9031-1},
	author = {Jain, Prashant K and Huang, Xiaohua and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {820,
	title = {Raman Studies on the Interaction of the Reactants with the Platinum Nanoparticle Surface during the Nanocatalyzed Electron Transfer Reaction},
	journal = {The Journal of Physical Chemistry B},
	volume = {109},
	year = {2005},
	note = {doi: 10.1021/jp053526k},
	month = {2005},
	pages = {18460 - 18464},
	publisher = {American Chemical Society},
	abstract = {Raman studies are conducted to understand the specific interactions between the individual reactants and the platinum nanoparticle surface during the nanocatalyzed electron transfer reaction between hexacyanoferrate (III) ions and thiosulfate ions. When Pt nanoparticles are added to the thiosulfate ion solution, a shift in the symmetric SS stretching mode is observed compared to the frequency observed for the free thiosulfate ions in solution, suggesting that binding to the Pt nanoparticle surface occurs via the S- ion. It is also observed that there are no shifts in the symmetric and asymmetric OSO bending or SO stretching frequencies. This suggests that the thiosulfate ions do not bind to the nanoparticle surface via the O- ion. When platinum nanoparticles are added to the hexacyanoferrate(III) ion solution, evidence is found for both adsorbed hexacyanoferrate(III) ions and a platinum cyanide complex. For adsorbed hexacyanoferrate(III) ions, the CN stretching frequency is observed at 2101 cm-1 and the Fe?C stretching frequency is found at 368 cm-1. The observed CN stretching frequencies located at 2147 and 2167 cm-1 provide strong evidence that there is a Pt(CN)42- platinum cyanide complex formed. In addition, the Pt?C?N band is also observed at 2054 cm-1. These observed bands provide spectroscopic evidence that the hexacyanoferrate(III) ions dissolve by forming a complex with the surface platinum atoms of the nanoparticles. Raman spectra of the product mixtures are obtained after the completion of the reaction when carried out with higher reactant concentrations to observe the Raman spectra, but with a similar 10:1 ratio of thiosulfate to hexacyanoferrate(III) ions as used previously, with and without PVP?Pt nanoparticles at a correspondingly higher concentration. It is observed that there are no shifts in the characteristic Raman bands associated with hexacyanoferrate(II) ions and no evidence for the formation of adsorbed hexacyanoferrate(II) species or platinum cyanide complexes in the presence of the platinum nanoparticles. In addition, there is evidence for the shifted symmetric SS stretching mode, suggesting that some of the unreacted thiosulfate (present in large excess) is bound to the Pt nanoparticle surface. Thus, under the actual reaction conditions, the hexacyanoferrate(III) ions preferentially react with adsorbed thiosulfate ions to form the reaction products, and this supports the surface catalytic mechanism we proposed previously.Raman studies are conducted to understand the specific interactions between the individual reactants and the platinum nanoparticle surface during the nanocatalyzed electron transfer reaction between hexacyanoferrate (III) ions and thiosulfate ions. When Pt nanoparticles are added to the thiosulfate ion solution, a shift in the symmetric SS stretching mode is observed compared to the frequency observed for the free thiosulfate ions in solution, suggesting that binding to the Pt nanoparticle surface occurs via the S- ion. It is also observed that there are no shifts in the symmetric and asymmetric OSO bending or SO stretching frequencies. This suggests that the thiosulfate ions do not bind to the nanoparticle surface via the O- ion. When platinum nanoparticles are added to the hexacyanoferrate(III) ion solution, evidence is found for both adsorbed hexacyanoferrate(III) ions and a platinum cyanide complex. For adsorbed hexacyanoferrate(III) ions, the CN stretching frequency is observed at 2101 cm-1 and the Fe?C stretching frequency is found at 368 cm-1. The observed CN stretching frequencies located at 2147 and 2167 cm-1 provide strong evidence that there is a Pt(CN)42- platinum cyanide complex formed. In addition, the Pt?C?N band is also observed at 2054 cm-1. These observed bands provide spectroscopic evidence that the hexacyanoferrate(III) ions dissolve by forming a complex with the surface platinum atoms of the nanoparticles. Raman spectra of the product mixtures are obtained after the completion of the reaction when carried out with higher reactant concentrations to observe the Raman spectra, but with a similar 10:1 ratio of thiosulfate to hexacyanoferrate(III) ions as used previously, with and without PVP?Pt nanoparticles at a correspondingly higher concentration. It is observed that there are no shifts in the characteristic Raman bands associated with hexacyanoferrate(II) ions and no evidence for the formation of adsorbed hexacyanoferrate(II) species or platinum cyanide complexes in the presence of the platinum nanoparticles. In addition, there is evidence for the shifted symmetric SS stretching mode, suggesting that some of the unreacted thiosulfate (present in large excess) is bound to the Pt nanoparticle surface. Thus, under the actual reaction conditions, the hexacyanoferrate(III) ions preferentially react with adsorbed thiosulfate ions to form the reaction products, and this supports the surface catalytic mechanism we proposed previously.},
	isbn = {1520-6106},
	doi = {10.1021/jp053526k},
	url = {http://dx.doi.org/10.1021/jp053526k},
	author = {Narayanan, Radha and El-Sayed, Mostafa A}
}
@article {845,
	title = {Relative enhancement of ultrafast emission in gold nanorods},
	journal = {The Journal of Physical Chemistry B},
	volume = {107},
	year = {2003},
	pages = {3101-3104},
	publisher = {ACS Publications},
	abstract = {Time-resolved fluorescence spectroscopy has been employed to probe the ultrafast emission observed in gold nanospheres and nanorods. The decay of the emission was found to be <=50 fs. The ultrafast emission from nanorods has been directly compared to that for nanospheres and the dispersion of the relative local field enhancement factor was obtained and compared with calculations. Measurements with both visible and ultraviolet excitations have been analyzed. These results give the first observation and analysis of the mechanism for the local field-enhanced ultrafast emission in gold nanorods and nanospheres.},
	isbn = {1520-6106},
	doi = {10.1021/jp0341265},
	url = {http://dx.doi.org/10.1021/jp0341265},
	author = {Varnavski, O. P. and Mohamed, MB and El-Sayed, Mostafa A and Goodson III, T.}
}
@article {1192,
	title = {Refolding of thermally denatured bacteriorhodopsin in purple membrane},
	journal = {Journal of Physical Chemistry B},
	volume = {106},
	number = {3},
	year = {2002},
	note = {Wang, JP Heyes, CD El-Sayed, MA},
	month = {Jan},
	pages = {723-729},
	abstract = {The change in protein conformational structure and retinal chromophore binding state have been examined by using in situ UV-vis, FTIR, and CD spectroscopies during the thermal denaturation and refolding processes in bacteriorhodopsin (bR) of purple membrane (PM), in its native trimeric and in Triton X-100 solubilized monomeric form. For the trimeric bR, it is found that heating bR through its premelting transition (T > 78 degreesC, T-m{\textquoteright}) does not cause any permanent damage in the protein secondary structure, and a reversible refolding occurs when it cools back to room temperature. For the monomeric bR, it is found that it is less thermally stable than the trimer. There is a significant change in its protein secondary structure and a complete dissociation of retinal occurs irreversibly at a temperature as low as 66 degreesC. In addition, it is found that heating the trimeric bR through its main molten state (T > 96 degreesC, T-m) changes the protein secondary structure so that bR does not refold fully into its original secondary structure. Upon cooling back to room temperature, about 90\% of the bound retinal in native bR recovers after being heated through its premelting transition, whereas only about 12\% of bound retinal recovers if bR is heated above its main melting temperature. It is also found that refolded bR molecules with their retinal chromophore rebound have a photocycle and are capable of pumping protons. Our results also suggest that from its molten state, protein secondary structure refolding precedes retinal rebinding to the Schiff base.},
	isbn = {1520-6106},
	doi = {10.1021/jp013131a},
	author = {Wang, Jianping and Heyes, C D and El-Sayed, Mostafa A}
}
@article {1203,
	title = {The role of the native lipids and lattice structure in bacteriorhodopsin protein conformation and stability as studied by temperature-dependent Fourier transform-infrared spectroscopy},
	journal = {Journal of Biological Chemistry},
	volume = {277},
	number = {33},
	year = {2002},
	note = {Heyes, CD El-Sayed, MA},
	month = {Aug},
	pages = {29437-29443},
	abstract = {We report the effect of partial delipidation and monomerization on the protein conformational changes of bacteriorhodopsin (bR) as a function of temperature. Removal of up to 75\% of the lipids is known to have the lattice structure of the purple membrane, albeit as a smaller unit cell, whereas treatment by Triton monomerizes bR into micelles. The effects of these modifications on the protein secondary structure is analyzed by monitoring the protein amide I and amide II bands in the Fourier transform-infrared (FT-IR) spectra. It is found that removal of the first 75\% of the lipids has only a slight effect on the secondary structure at physiological temperature, whereas monomerizing bR into micelles alters the secondary structure considerably. Upon heating, the bR monomer is found to have a very low thermal stability compared with the native bR with its melting point reduced from 97 to 65 degreesC, and the premelting transition in which the protein changes conformation in native bR at 80 degreesC could not be observed. Also, the N-H to N-D exchange of the amide II band is effectively complete at room temperature, suggesting that there are no hydrophobic regions that are protected from the aqueous medium, possibly explaining the low thermal stability of the monomer. On the other hand, 75\% delipidated bR has its melting temperature close to that of the native bR and does have a pre-melting transition, although the pre-melting transition occurs at significantly higher temperature than that of the native bR (91 degreesC compared with 80 degreesC) and is still reversible. Furthermore, we have also observed that the reversibility of this pre-melting transition of both native and partially delipidated bR is time-dependent and becomes irreversible upon holding at 91 degreesC between 10 and 30 min. These results are discussed in terms of the lipid and lattice contribution to the protein thermal stability of native bR.},
	isbn = {0021-9258},
	doi = {10.1074/jbc.M203435200},
	author = {Heyes, C D and El-Sayed, Mostafa A}
}
@article {1198,
	title = {Room temperature optical gain in CdSe nanorod solutions},
	journal = {Journal of Applied Physics},
	volume = {92},
	number = {11},
	year = {2002},
	note = {Link, S El-Sayed, MA},
	month = {Dec},
	pages = {6799-6803},
	abstract = {We have performed femtosecond transient absorption measurements on CdSe nanorods in hexane solution as a function of pump wavelength and pump intensity. We found that although it is not possible to achieve optical gain when pumping at energies (400 nm) high above the band-gap energy, this problem can be circumvented by pumping the CdSe nanorods directly at the lowest 1S transition. We attribute the difference to alternative relaxation pathways and possibly trapping, resulting in a competing induced absorption below the band-gap energy when excitation is carried out at high energies. Our results suggest that it is possible to achieve stimulated emission from CdSe nanoparticles in solution at ambient temperature if the excitation wavelength is chosen properly. (C) 2002 American Institute of Physics.},
	isbn = {0021-8979},
	doi = {10.1063/1.1512689},
	author = {Link, Stephan and El-Sayed, Mostafa A}
}
@article {1211,
	title = {The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {98},
	number = {15},
	year = {2001},
	note = {Logunov, SL Volkov, VV Braun, M El-Sayed, MA},
	month = {Jul},
	pages = {8475-8479},
	abstract = {We present the results of two-pump and probe femtosecond experiments designed to follow the relaxation dynamics of the lowest excited state (S-1) populated by different modes. In the first mode, a direct (S-0 --> S-1) radiative excitation of the ground state is used. In the second mode, an indirect excitation is used where the S-1 state is populated by the use of two femtosecond laser pulses with different colors and delay times between them. The first pulse excites the S-0 --> S-1 transition whereas the second pulse excites the S-1 --> S-n transition. The nonradiative relaxation from the S-n state populates the lowest excited state. Our results suggest that the S1 state relaxes faster when populated nonradiatively from the S-n state than when pumped directly by the S-0 --> S-1 excitation. Additionally, the S-n --> S-1 nonradiative relaxation time is found to change by varying the delay time between the two pump pulses. The observed dependence of the lowest excited state population as well as its dependence on the delay between the two pump pulses are found to fit a kinetic model in which the S-n state populates a different surface (called Si) than the one being directly excited (S-1). The possible involvement of the A(g) type states, the J intermediate, and the conical intersection leading to the S-0 or to the isomerization product (K intermediate) are discussed in the framework of the proposed model.},
	isbn = {0027-8424},
	doi = {10.1073/pnas.141220198},
	author = {Logunov, Stephan L. and Volkov, V. V. and Braun, Markus and El-Sayed, Mostafa A}
}
@article {1260,
	title = {Redetermination of the Quantum Yield of Photoisomerization and Energy Content in the K-Intermediate of Bacteriorhodopsin Photocycle and Its Mutants by the Photoacoustic Technique},
	journal = {The Journal of Physical Chemistry B},
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp970955c},
	month = {1997},
	pages = {6629 - 6633},
	publisher = {American Chemical Society},
	abstract = {Data obtained previously in our lab for the quantum yield retinal photoisomerization and the energy content of the K-intermediate formed in the bacteriorhodopsin and its mutants (bR) photocycle are reexamined using time-resolved transient spectroscopy and laser-induced photoacoustic spectroscopy. In the present experiment both nanosecond and subpicosecond laser pulses are used for excitation, with different reference compounds. From these new results it can be concluded that using CoCl2 as a reference compound in the photoacoustic experiment with subpicosecond laser pulses gives a large amount of prompt heat release resulting from multiphoton absorption processes. This results in an overestimated energy content of the K-intermediate of bR and its mutants. Using different reference compounds, the corrected values are 40 {\textpm} 10 kJ/mol, which is in agreement with previously reported values. The apparent quantum yield and energy content values (for each of the isomeric compositions) of the mutants D212N, D85N, R82Q, A53G, W182F, V49A, deionized blue bR, and acid purple bR are also recalculated using bR as a reference compound and are similar to those of bR. (Φ is in the range 0.55?0.65, and EK is in the range 40?50 kJ/mol.) The relative insensitivity of the apparent average quantum yield value is discussed.Data obtained previously in our lab for the quantum yield retinal photoisomerization and the energy content of the K-intermediate formed in the bacteriorhodopsin and its mutants (bR) photocycle are reexamined using time-resolved transient spectroscopy and laser-induced photoacoustic spectroscopy. In the present experiment both nanosecond and subpicosecond laser pulses are used for excitation, with different reference compounds. From these new results it can be concluded that using CoCl2 as a reference compound in the photoacoustic experiment with subpicosecond laser pulses gives a large amount of prompt heat release resulting from multiphoton absorption processes. This results in an overestimated energy content of the K-intermediate of bR and its mutants. Using different reference compounds, the corrected values are 40 {\textpm} 10 kJ/mol, which is in agreement with previously reported values. The apparent quantum yield and energy content values (for each of the isomeric compositions) of the mutants D212N, D85N, R82Q, A53G, W182F, V49A, deionized blue bR, and acid purple bR are also recalculated using bR as a reference compound and are similar to those of bR. (Φ is in the range 0.55?0.65, and EK is in the range 40?50 kJ/mol.) The relative insensitivity of the apparent average quantum yield value is discussed.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp970955c},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A}
}
@article {861,
	title = {Replacement effects of neutral amino acid residues of different molecular volumes in the retinal binding cavity of bacteriorhodopsin on the dynamics of its primary process.},
	journal = {Biophysical journal},
	volume = {70},
	year = {1996},
	month = {1996 Jun},
	pages = {2875-81},
	abstract = {We have determined the rate and quantum yield of retinal photoisomerization, the spectra of the primary transients, and the energy stored in the K intermediate in the photocycle of some bacteriorhodopsin mutants (V49A, A53G, and W182F) in which residue replacements are found to change the Schiff base deprotonation kinetics (and thus the protein-retinal interaction). Because of their change in the local volume resulting from these individual replacements, these substitutions perturb the proton donor-acceptor relative orientation change and thus the Schiff base deprotonation kinetics. These replacements are thus expected to change the charge distribution around the retinal, which controls its photoisomerization dynamics. Subpicosecond transient spectroscopy as well as photoacoustic technique are used to determine the retinal photoisomerization rate, quantum yield, and the energy stored in the K-intermediate for these mutants. The results are compared with those obtained for wild-type bacteriorhodopsin and other mutants in which charged residues in the cavity are replaced by neutral ones. In some of the mutants the rate of photoisomerization is changed, but in none is the quantum yield or the energy stored in the K intermediate altered from that in the wild type. These results are discussed in terms of the shapes of the potential energy surfaces of the excited and ground states of retinal in the perpendicular configuration within the protein and the stabilization of the positive charge in the ground and the excited state of the electronic system of retinal.},
	keywords = {Bacteriorhodopsins, Binding Sites, Biophysical Phenomena, Biophysics, Halobacterium salinarum, Kinetics, Mutagenesis, Site-Directed, Photochemistry, Quantum Theory, Retinaldehyde, Schiff Bases},
	issn = {0006-3495},
	doi = {10.1016/S0006-3495(96)79857-0},
	author = {Logunov, Stephan L. and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {1268,
	title = {Retinal Isomer Composition in Some Bacteriorhodopsin Mutants under Light and Dark Adaptation Conditions},
	journal = {The Journal of Physical Chemistry},
	volume = {99},
	year = {1995},
	note = {doi: 10.1021/j100024a056},
	month = {1995},
	pages = {10052 - 10055},
	publisher = {American Chemical Society},
	abstract = {View http://dx.doi.org/10.1021/j100024a056 for the article{\textquoteright}s first page in lieu of an abstract},
	isbn = {0022-3654},
	doi = {doi: 10.1021/j100024a056},
	url = {http://dx.doi.org/10.1021/j100024a056},
	author = {Song, Li and Yang, Difei and El-Sayed, Mostafa A and Lanyi, Janos K.}
}
@article {1280,
	title = {Recording of transient gratings using the short lived bacteriorhodopsin photocycle intermediates},
	journal = {Advanced Materials},
	volume = {5},
	year = {1993},
	month = {1993},
	pages = {838 - 842},
	publisher = {WILEY-VCH Verlag GmbH},
	abstract = {Bacteriorhodopsin, a light-transducing protein in the purple membrane of Halobacterium halobium, has unique properties that make it a potentially attractive material for use in optical imaging and processing. A transient diffraction grating based on the K intermediate of the bacteriorhodopsin photocycle has been produced on the nanosecond time scale. The diffraction efficiency, which would be sufficient for pattern recognition for example, was measured and the intensity dependence assessed.},
	isbn = {1521-4095},
	doi = {10.1002/adma.19930051111},
	url = {http://dx.doi.org/10.1002/adma.19930051111},
	author = {Wu, Shuguang and Br{\"a}uchle, Christoph and El-Sayed, Mostafa A}
}
