@article {1084,
	title = {Multimodal plasmon coupling in low symmetry gold nanoparticle pairs detected in surface-enhanced Raman scattering},
	journal = {Applied Physics Letters},
	volume = {98},
	number = {18},
	year = {2011},
	note = {Dreaden, Erik C. Near, Rachel D. Abdallah, Tamer Talaat, M. Hassan El-Sayed, Mostafa A.},
	month = {May},
	abstract = {We report on surface-enhanced Raman scattering of silicon phonon vibrations from arrays of gold nanoprism pairs fabricated by electron beam lithography. We found that resonant excitation of the quadrupolar surface plasmon mode of the nanoprisms increases Raman scattering intensity from the substrate as the distance between the nanoparticle pairs decreases. Finite element modeling and plasmon coupling theory indicate that symmetry is reduced as the nanoparticles approach, resulting in increased dipole-quadrupole coupling. Plasmonic enhancement of the incident and Raman-scattered photons results from the dipolar component of the mixed plasmonic field. This effect is expected to be largest in assemblies/aggregates of nanoparticles. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555429]},
	isbn = {0003-6951},
	doi = {10.1063/1.3555429},
	author = {Dreaden, Erik and Near, R. D. and Abdallah, T. and Talaat, M. H. and El-Sayed, Mostafa A}
}
@article {1100,
	title = {On the Mechanism of the Plasmonic Field Enhancement of the Solar-to-Electric Energy Conversion by the Other Photosynthetic System in Nature (Bacteriorhodopsin): Kinetic and Spectroscopic Study},
	journal = {Journal of Physical Chemistry C},
	volume = {114},
	number = {36},
	year = {2010},
	note = {Chu, Li-Kang Yen, Chun-Wan El-Sayed, Mostafa A.},
	month = {Sep},
	pages = {15358-15363},
	abstract = {We have recently reported Ag nanoparticles (AgNPs) plasmonic field enhancement of the Bacteriorhodopsin (bR) photocurrent observed during its proton pump photocycle in solution. We proposed a mechanism based on the plasmonic field enhancement of the blue light effect which bypasses the slow part of the photocycle and increases the rate of proton production and thus the observed photocurrent. In this present work, we studied the AgNPs plasmonic field effect on the spectroscopy and kinetics of the bR proton pumping photocycle. We examined the blue light effect on both the recovery rate of bR and the decay rate of the M intermediate by using 532-nm short-pulsed laser excitation of bR in the presence of AgNPs and continuous-wave blue light exposure. Our observation showed that the recovery of bR and the decay of the M intermediate are both greatly accelerated in the presence of both AgNPs and blue light simultaneously. This gives support for the proposed mechanism of the enhanced proton current in the presence of AgNPs with a plasmon band in the blue region. It was found experimentally that the 40 nm-AgNPs enhancement of the blue light effect on the decay rate is around 400x larger than that of 8 nm-AgNPs. This is found to be in agreement with the known dependence of the plasmonic field on size and the overlap of the plasmonic extinction band with the absorption band of the M intermediates.},
	isbn = {1932-7447},
	doi = {10.1021/jp105468x},
	author = {Chu, L. K. and Yen, C. W. and El-Sayed, Mostafa A}
}
@article {1294,
	title = {Multicolorimetric plasmonic gold nanoparticles for 8 optical detection of oral squamous carcinoma},
	journal = {Oral Oncology},
	volume = {43},
	year = {2007},
	note = {El-Sayed, I. Huang, X. El-Sayed, M.1st World Congress of the International-Academy-of-Oral-OncologyMay 17-20, 2007Amsterdam, NETHERLANDSInt Acad Oral OncolS},
	month = {05/2007},
	pages = {121-121},
	issn = {1368-8375},
	author = {El Sayed, I.H. and Huang, X. and El-Sayed, Mostafa A}
}
@article {1157,
	title = {Molecular mechanism of the photochemical generation of gold nanoparticles in ethylene glycol: Support for the disproportionation mechanism},
	journal = {Journal of Physical Chemistry B},
	volume = {110},
	number = {29},
	year = {2006},
	note = {Eustis, Susie El-Sayed, Mostafa A.},
	month = {Jul},
	pages = {14014-14019},
	abstract = {It is found that replacement of the chloride ions in tetrachloroauric acid with bulky bromide ions inhibits the formation of gold nanoparticles in the photochemical reduction in ethylene glycol. However, the addition of silver ions to either the bromide or the chloride auric acid solution is found to enhance the rate of gold nano-particle formation. These results are found to be accounted for by the previously proposed mechanism (Eustis, S.; Hsu, H.-Y.; El-Sayed, M. A. J. Phys. Chem. B 2005, 109, 4811) which involves disproportionation of the chloroauric complexes to generate free gold atoms and chloride ions. The steric effects of the bulky bromide ions inhibit the formation of the Au-Au bond needed in the electron transfer process of the disproportionation reaction. The addition of Ag(+) ions results in the formation of insoluble silver halide, which shifts the disproportionation reaction toward the formation of gold atoms and thus the formation of gold nanoparticles.},
	isbn = {1520-6106},
	doi = {10.1021/jp062972k},
	author = {Eustis, Susie and El-Sayed, Mostafa A}
}
@article {1183,
	title = {Model system for growing and quantifying Streptococcus pneumoniae biofilms in situ and in real time},
	journal = {Applied and Environmental Microbiology},
	volume = {70},
	number = {8},
	year = {2004},
	note = {Donlan, RM Piede, JA Heyes, CD Sanii, L Murga, R Edmonds, P El-Sayed, I El-Sayed, MA},
	month = {Aug},
	pages = {4980-4988},
	abstract = {Streptococcus pneumoniae forms biofilms, but little is known about its extracellular polymeric substances (EPS) or the kinetics of biofilm formation. A system was developed to enable the simultaneous measurement of cells and the EPS of biofilm-associated S. pneumoniae in situ over time. A biofilm reactor containing germanium coupons was interfaced to an attenuated total reflectance (ATR) germanium cell of a Fourier transform infrared (FTIR) laser spectrometer. Biofilm-associated cells were recovered from the coupons and quantified by total and viable cell count methods. ATR-FTIR spectroscopy of biofilms formed on the germanium internal reflection element (IRE) of the ATR cell provided a continuous spectrum of biofilm protein and polysaccharide (a measure of the EPS). Staining of the biofilms on the IRE surface with specific fluorescent probes provided confirmatory evidence for the biofilm structure and the presence of biofilm polysaccharides. Biofilm protein and polysaccharides were detected within hours after inoculation and continued to increase for the next 141 h. The polysaccharide band increased at a substantially higher rate than did the protein band, demonstrating increasing coverage of the IRE surface with biofilm polysaccharides. The biofilm total cell counts on germanium coupons stabilized after 21 h, at approximately 10(5) cells per cm(2), while viable counts decreased as the biofilm aged. This system is unique in its ability to detect and quantify biofilm-associated cells and EPS of S. pneumoniae over time by using multiple, corroborative techniques. This approach could prove useful for the study of biofilm processes of this or other microorganisms of clinical or industrial relevance.},
	isbn = {0099-2240},
	doi = {10.1128/aem.70.8.4980-4988.2004},
	author = {Donlan, R. M. and Piede, J. A. and Heyes, C D and Sanii, L. S. and Murga, R. and Edmonds, P. and El Sayed, I.H. and El-Sayed, Mostafa A}
}
@article {1187,
	title = {Medium effect on the electron cooling dynamics in gold nanorods and truncated tetrahedra},
	journal = {Advanced Materials},
	volume = {15},
	number = {5},
	year = {2003},
	note = {Link, S Hathcock, DJ Nikoobakht, B El-Sayed, MA},
	month = {Mar},
	pages = {393-+},
	abstract = {A study on the electron relaxation dynamics and thermal cooling of colloidal gold nanoparticles (see Figure) in air and water finds that the local energy exchange with the surrounding medium occurs on the picosecond time scale, comparable with the electron-phonon relaxation, while a slow heat dissipation by water ensures that the particles remain heated for hundreds of picoseconds.},
	isbn = {0935-9648},
	doi = {10.1002/adma.200390088},
	author = {Link, Stephan and Hathcock, D. J. and Nikoobakht, Babak and El-Sayed, Mostafa A}
}
@article {874,
	title = {Molecular Mechanism of the Differential Photoelectric Response of Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry B },
	volume = {101},
	year = {1997},
	note = {doi: 10.1021/jp962111j},
	month = {1997},
	pages = {3420 - 3423},
	publisher = {American Chemical Society},
	abstract = {In order to determine the molecular origin of the differential photocurrent from bacteriorhodopsin (bR), the photoelectric response of bR film deposited on an indium tin oxide (ITO) conductive glass electrode under CW excitation is compared with that under pulsed laser excitation at different pH and with opposite membrane orientation with respect to the ITO electrode surface. The characteristics (sign and magnitude) of the dominant component of the differential photocurrent (appearing on the millisecond time scale) are found to correlate with the process of proton release into, or uptake from, the aqueous solution during the photocycle under different experimental conditions. This suggests that the differential current results mainly from the change in the H+ concentration at the bR?ITO electrode interface.In order to determine the molecular origin of the differential photocurrent from bacteriorhodopsin (bR), the photoelectric response of bR film deposited on an indium tin oxide (ITO) conductive glass electrode under CW excitation is compared with that under pulsed laser excitation at different pH and with opposite membrane orientation with respect to the ITO electrode surface. The characteristics (sign and magnitude) of the dominant component of the differential photocurrent (appearing on the millisecond time scale) are found to correlate with the process of proton release into, or uptake from, the aqueous solution during the photocycle under different experimental conditions. This suggests that the differential current results mainly from the change in the H+ concentration at the bR?ITO electrode interface.},
	isbn = {1520-6106},
	url = {http://dx.doi.org/10.1021/jp962111j},
	author = {Wang, Jianping and Yoo, Seoung-Kyo and Song, Li and El-Sayed, Mostafa A}
}
@article {1289,
	title = {On the molecular origin of the protein catalysis of the primary process in bacteriorhodopsin photosynthesis: Retinal photoisomerization},
	journal = {Pure and Applied Chemistry},
	volume = {69},
	number = {4},
	year = {1997},
	note = {Times Cited: 816th IUPAC Symposium on PhotochemistryJul 21-26, 1996Helsinki, finlandIupac},
	month = {Apr},
	pages = {749-754},
	abstract = {Using subpicosecond transient optical absorption spectroscopic techniques, the photoisomerization rates and quantum yields were determined for. bacteriorhodopsin, its relevant mutants, its dionized form and at different pH and Cl- concentrations. It is found that the rate is catalyzed and made highly specific around the C-13-C-14 bond by the presence of negative charges within the retinal cavity (e.g., Asp85 and Asp 212). Any perturbation that genetically removes, acid neutralizes, or changes the geometry of these negative charges is found to decrease the tate of photoisomerization, but does not greatly change its quantum yield. These results sue discussed in terms of the changes in the electronic structure of the retinal as well as in the anisotropic charge distribution within the cavity that result from the photoexcitation process. The different potential energy surfaces proposed to explain the dynamics of the photoisomerization process are examined in terms of our observed results.},
	isbn = {0033-4545},
	doi = {10.1351/pac199769040749},
	author = {El-Sayed, Mostafa A and Logunov, Stephan L.}
}
@article {1271,
	title = {Monodentate vs Bidentate Binding of Lanthanide Cations to PO2- in Bacteriorhodopsin},
	journal = {The Journal of Physical Chemistry},
	volume = {100},
	year = {1996},
	note = {doi: 10.1021/jp9533279},
	month = {1996},
	pages = {6863 - 6866},
	publisher = {American Chemical Society},
	abstract = {The frequency difference between the symmetric and antisymmetric stretching vibration of PO2- in phosphatidylglycerol phospate (PGP) is used to differentiate between monodentate and bidentate binding of these groups to metal cations in the membrane of bacteriorhodopsin (bR) and phosphatidylglycerol phospate. The binding of Ca2+ to PGP is found to have a frequency difference corresponding to monodentate binding. The symmetric and antisymmetric PO2- bands in bR show similar frequency shifts upon Ca2+ binding, which is independent of pH. This suggests that Ca2+ has a monodentate type binding with the PO2- in bR. In contrast, the PO2- symmetric and antisymmetric frequencies of PGP complexes with trivalent lanthanide cations with higher charge density (Ho3+ and Dy3+) are observed to have smaller separations and to increase their separation with increasing pH toward the value observed for Ca2+ binding. Lanthanide cations (Ho3+, Dy3+, Eu3+, Nd3+, and La3+) binding in bR at pH 4 show small frequency separations that are observed to have similar frequency shifts with pH, the magnitude of which is dependent on the cation. It is proposed that at low pH the lanthanide cations with higher charge density have bidentate binding to bR, while at high pH, complexation with the OH- competes with one of the oxygens of the PO2- for the binding of the lanthanide ion thus changing the bidentate to monodentate type binding.The frequency difference between the symmetric and antisymmetric stretching vibration of PO2- in phosphatidylglycerol phospate (PGP) is used to differentiate between monodentate and bidentate binding of these groups to metal cations in the membrane of bacteriorhodopsin (bR) and phosphatidylglycerol phospate. The binding of Ca2+ to PGP is found to have a frequency difference corresponding to monodentate binding. The symmetric and antisymmetric PO2- bands in bR show similar frequency shifts upon Ca2+ binding, which is independent of pH. This suggests that Ca2+ has a monodentate type binding with the PO2- in bR. In contrast, the PO2- symmetric and antisymmetric frequencies of PGP complexes with trivalent lanthanide cations with higher charge density (Ho3+ and Dy3+) are observed to have smaller separations and to increase their separation with increasing pH toward the value observed for Ca2+ binding. Lanthanide cations (Ho3+, Dy3+, Eu3+, Nd3+, and La3+) binding in bR at pH 4 show small frequency separations that are observed to have similar frequency shifts with pH, the magnitude of which is dependent on the cation. It is proposed that at low pH the lanthanide cations with higher charge density have bidentate binding to bR, while at high pH, complexation with the OH- competes with one of the oxygens of the PO2- for the binding of the lanthanide ion thus changing the bidentate to monodentate type binding.},
	isbn = {0022-3654},
	doi = {doi: 10.1021/jp9533279},
	url = {http://dx.doi.org/10.1021/jp9533279},
	author = {Griffiths, Jennifer A. and Masciangioli, Tina M. and Roselli, Cecile and El-Sayed, Mostafa A}
}
@article {1283,
	title = {On the molecular mechanisms of the rapid and slow solar-to-electric energy storage processes by the other natural photosynthetic system, bacteriorhodopsin},
	journal = {Pure and applied chemistry},
	volume = {67},
	year = {1995},
	pages = {149-149},
	publisher = {BLACKWELL SCIENTIFIC PUBLICATIONS},
	abstract = {Upon the absorption of solar energy by retinal in bacterioi..>dopsin highly specific photoisomerization of the retinal around the C13 -C14 bond takes place. This is followed by the formation of a number of intermediates resulting from conformational changes of the protein around the retinal which leads to the deprotonation of the protonated Schiff base of the retinylidene system. Thisis the switch of the proton pump which leads to the last step in the storage of solar energy in the form of electric energy by this photosynthetic system. The removal of metal cations from bR is found to inhibit the deprotonation process.
In the present paper we summarize the results of our studies and the others regarding two important questions in the conversion process: 1) what is(are) the molecular mechanism(s) of the protein catalysis of the photoisomerizationprocess and 2) what is the role of metal cations in the deprotonation process of the protonated Schiff base (the switch of the proton pump)? In order to answer the first question, the results of the subpicosecondphotoisomerization rate of retinal in bR and in a number of its relevant mutants are discussed in terms of the steric and electronic factors. In an effort to answer the second question,we discussed the results of the binding studies of Ca*+to bR, to its mutants and to bR after its C- terminus is cleaved. From these results and the results of Roux et al. on the 31P NMR of Nd3+ regenerated bR, we concluded that one or two metal cations strongly bound to the protein but not on the surface, are functionally important. The model in which these metal cation@)control the pK values of Aspartic acids in the 85 and 212 positions and that of the protonated Schiff base (PSB) during the photocycle is discussed.},
	isbn = {0033-4545},
	author = {El-Sayed, Mostafa A and Griffiths, Jennifer A. and Song, Li and Zhang, N.}
}
