Surface-Enhanced Resonance Raman Spectroscopy Signals from Single Myoglobin Molecules (original) (raw)
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Spectroscopy of single hemoglobin molecules by surface enhanced Raman scattering
Physical review letters, 1999
We demonstrate the detection of molecular vibrations in single hemoglobin (Hb) protein molecules attached to isolated and immobilized silver nanoparticles by surface enhanced Raman scattering (SERS). A comparison between calculation and experiment indicates that electromagnetic field effects dominate the surface enhancement, and that single molecule Hb SERS is possible only for molecules situated between Ag particles. The vibrational spectra exhibit temporal fluctuations of unknown origin which appear to be characteristic of the single molecule detection limit.
Journal of Physics: Condensed Matter, 2007
Using surface enhanced ROA (SEROA), novel results are achieved by combining Raman optical activity (ROA) and resonance surface enhanced Raman scattering (SERRS), applied on myoglobin. The novelty of this work is in reporting for the first time on chiral results of a study performed on a protein at single molecule level. This work, using silver nanoparticles and a laser excitation of 532 nm, only became feasible when the concentrations of nanoparticles, aggregation agent NaCl and the studied molecule were optimized in a series of systematic optimization steps. The spectral analysis has shown that the SERS effect behaves accordingly, depending on the concentration ratio of each component, i.e., myoglobin, Ag colloids and NaCl. Consequently, it is shown here that the SERS intensity has its maximum at a certain concentration of these components, whereas below or above this value the intensity decreases. The optimization results can be considered as a completion of the hitherto known phenomenon 'dilution effect', which only takes account of higher concentrations. Furthermore, the optimization of the parameters seems to be necessary for a successful SEROA measurement, which enables chiral study of a protein at the single molecule level, in which the concentration and acquisition time are no longer an impediment.
Surface Enhanced Raman Optical Effect as a Function of Ag-Colloids, NaCl and Myoglobin Concentration
2007
Using surface enhanced ROA (SEROA), novel results are achieved by combining Raman optical activity (ROA) and resonance surface enhanced Raman scattering (SERRS), applied on myoglobin. The novelty of this work is in reporting for the first time on chiral results of a study performed on a protein at single molecule level. This work, using silver nanoparticles and a laser excitation of 532 nm, only became feasible when the concentrations of nanoparticles, aggregation agent NaCl and the studied molecule were optimized in a series of systematic optimization steps. The spectral analysis has shown that the SERS effect behaves accordingly, depending on the concentration ratio of each component, i.e., myoglobin, Ag colloids and NaCl. Consequently, it is shown here that the SERS intensity has its maximum at a certain concentration of these components, whereas below or above this value the intensity decreases. The optimization results can be considered as a completion of the hitherto known phenomenon 'dilution effect', which only takes account of higher concentrations. Furthermore, the optimization of the parameters seems to be necessary for a successful SEROA measurement, which enables chiral study of a protein at the single molecule level, in which the concentration and acquisition time are no longer an impediment.
Biosensors and Bioelectronics, 2006
The extremely large cross-section available from metallic surface enhancement has been exploited to investigate the Raman spectrum of heme myoglobin adsorbed on silver colloidal nanoparticles at very low concentrations. The study has been performed on particles both in solution and immobilized onto a polymer-coated glass surface. In both the cases, we have observed striking temporal uctuations in the surface-enhanced resonance Raman spectroscopy (SERRS) spectra collected at short tim es. A statistical analysis of the temporal intensity uctuations and of the associated correlations of the Raman signals has allowed us to verify that the single molecule limit is approached. The possible connections of these uctuations with the entanglement of the biomolecule within the local minima of its rough energy landscape is discussed.
Chirality, 2009
The metalloprotein hemoglobin (Hb) was studied using surface enhanced resonance Raman spectroscopy (SERRS) and surface enhanced resonance Raman optical activity (SERROA). The SERROA results are analyzed and compared with the SERRS, and the later to the resonance Raman (RRS) performed on Hb. The SERRS measurements careful optimization, with respect to the concentration and volume ratio of the analyte to colloids, enables for the first time SERROA of this molecule. We observed that the most intense SERROA signals were attributed the m 4 , m 20 , and m 21 vibrations, which are sensitive to the redox state of the heme's iron ion, and to the presence of its sixth site, bound to exogenous ligand; O 2 , NO or CO. However, in this study, the SERROA signals corresponding to these vibrations appear more sensitive to the Hb oxygen-binding properties than they appear in the SERRS or RRS. Moreover, the SER-ROA signal of Hb has successfully been monitored as a function of time, and was observed to be stable for 4-5 min. To our knowledge, the SERROA results of Hb, and its comparison to SERRS and RRS, are here reported for the first time. Chirality 21:S307-S312, 2009. V V C 2010 Wiley-Liss, Inc.
Hemoglobin detection on AgO surface enhanced Raman scattering (SERS)-substrates
2014
Human hemoglobin (2.2×10−4 M) detection has been demonstrated on AgO surface enhanced Raman scattering (SERS)-substrates. Hot spots that enable detection of hemoglobin using SERS are formed at the silver nanoclusters induced by the photo-activation of AgO under Raman excitation wavelength (633 nm). Higher enhancement is observed at integration time (20 s) and threshold energy density (12 M J/cm2). At higher excitation energy densities photo-chemical (or photo-thermal) activity of the hemoglobin molecules are dominated. These results are critical to the future use of AgO films as SERS substrates for the detection of biological molecules.
Probing Single Molecules and Single Nanoparticles by Surface-Enhanced Raman Scattering
Science, 1997
Optical detection and spectroscopy of single molecules and single nanoparticles have been achieved at room temperature with the use of surface-enhanced Raman scattering. Individual silver colloidal nanoparticles were screened from a large heterogeneous population for special size-dependent properties and were then used to amplify the spectroscopic signatures of adsorbed molecules. For single rhodamine 6G molecules adsorbed on the selected nanoparticles, the intrinsic Raman enhancement factors were on the order of 10 14 to 10 15 , much larger than the ensemble-averaged values derived from conventional measurements. This enormous enhancement leads to vibrational Raman signals that are more intense and more stable than single-molecule fluorescence.
Raman spectroscopy and silver nanoparticles in biomedical studies of hemoglobin
Moscow University Chemistry Bulletin, 2015
Raman spectroscopy (RS) in conjunction with silver nanoparticles (SNPs) is a sensitive method for diagnostics of hemoglobin in biomedicine. It is shown that the applicability of this method with the injec tion of SNPs into the body is limited due to adverse effects on the capacity of hemoglobin to transport O 2. The use of nanostructured silver substrates is a more effective and native way to study hemoglobin conforma tion without requiring injection of SNPs into the body.
Journal of Luminescence, 2001
Surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) adsorbed on isolated colloidal silver clusters has been studied down to the single-molecule level with a high-resolution confocal optical microscope equipped with a spectrometer and a cooled CCD-camera. At the single-molecule level the SERRS-spectra recorded as a function of time reveal inhomogeneous behaviour such as on/off blinking, spectral diffusion and intensity fluctuations of vibrational lines, and even splitting of some lines within the spectrum of one molecule. r
New Insight into Erythrocyte through In Vivo Surface-Enhanced Raman Spectroscopy
Biophysical Journal, 2009
The article presents a noninvasive approach to the study of erythrocyte properties by means of a comparative analysis of signals obtained by surface-enhanced Raman spectroscopy (SERS) and resonance Raman spectroscopy (RS). We report step-by-step the procedure for preparing experimental samples containing erythrocytes in their normal physiological environment in a mixture of colloid solution with silver nanoparticles and the procedure for the optimization of SERS conditions to achieve high signal enhancement without affecting the properties of living erythrocytes. By means of three independent techniques, we demonstrate that under the proposed conditions a colloid solution of silver nanoparticles does not affect the properties of erythrocytes. For the first time to our knowledge, we describe how to use the SERS-RS approach to study two populations of hemoglobin molecules inside an intact living erythrocyte: submembrane and cytosolic hemoglobin (Hb sm and Hb c ). We show that the conformation of Hb sm differs from the conformation of Hb c . This finding has an important application, as the comparative study of Hb sm and Hb c could be successfully used in biomedical research and diagnostic tests.