Characteristics of SERS

Classification, Structure and Characteristics of Ser/Thr-specific Protein Kinases... 

Another interesting characteristic of SERS is that, as was shown above, in many systems special sites are most efficient in promoting it. Thus, generally, SERS does not see all the molecules, but mainly those adsorbed near surface defects. But these same defects and sites may be the center of the chemical activity of the surface. It would be of extreme importance if such a connection could be made, and future research in this direction may prove very fruitful. Knoll et have shown that IR and SERS are sensitive to molecules in different environments on the same system. Also, Yamada et al found for CO on silver that the IR exhibited a band at 1940 cm while in SERS a band at 2112 cm" was observed. Consequently, these two methods are complementary also on the surface. 

Experimental Characteristics of SERS Since the mid-1970s when the first SERS spectrum was obtained from an electrochemical cell, a large number of experimental characteristics of SERS have been discovered, and the key features are summarized as follows [6, 7,12-14, 24] ... 

In fact, the possibility of obtaining molecular structural information from the target analyte inside the cell is the most important characteristic of SERS. Until now this has not been possible by any other techniques. On the other hand, the limitation of intracellular SERS spectroscopy exists due to the complex matrix of molecules present in the cell that can produce SERS. Consequentiy, very complicated SERS spectra are acquired from the cells. Such SERS spectra provide only general information about the types of molecules present inside the cell. Therefore, in order to obtain a specific and known SERS spectmm from cells functionalization of the SERS tags with a RRM is required. 

As a prelude to our binding studies, the secondary structure of aPNA itself was examined using CD spectroscopy [52]. The first aPNA to be studied was the tail-to-tail bl dimer, [Ac-Cys-Gly-Ser -Asp-Ala-Glu-Ser -Ala-Ala-Lys-Ser -Ala-Ala-Glu-Ser -Ala-Aib-Ala-Ser -Lys-Gly-NH2]2- The far-UV CD spectra of this aPNA in water at 30 °C showed the double minimum at 220 nm (n-n transition) and 206 nm (n-n transition) as well as the maximum at 193 nm (n-n transition), characteristic of a peptide a-hehx. Upon increasing the temperature, the intensity of the minimum at 200 nm decreased indicating a transition from a-helix to random stracture. An isodichroic point at 202 nm was suggestive of a temperature-depen-dent a-helix to random coil transition. The helical content of this T5(bl)-dimer at 20°C in water was estimated to be 26% [40]. 

Palen, J. W., Yarden, A. and Taborek, J. (1972) Chem. Eng. Symp. Ser. No. 118, 68, 50. Characteristics of boiling outside large-scale horizontal multitube boilers. 

Poulson, R.E. Frost, C.M. Jensen, H.B. Characteristics of Synthetic Crude from Crude Shale Oil Produced by In-situ Combustion Retorting, In Shale Oil, Tar Sands, and Related Fuel Sources Yen, T.F., Ed ACS Adv. Chem. Ser. No. 151, 1976, 1. 

Physico-chemical characteristics of the soils were summarized in Table 1. The values were comparable to that described in the previous reports about the SERS (Doi and Sakurai 2003 Doi et al. 2004 Sakurai et al. 1998). The one-way ANOVA indicated that most of the soil variables significantly reflected the land degradation with high values of bulk density, sand content and exchangeable acidity, and low values of moisture content, pH, OM, base (K, Ca, Mg) contents, EC, CEC, base saturation rate, TN and TC contents, available phosphorus and MPN on the glucose medium with no antibiotics. These results also told that the human activities induced several soil environmental gradients. 

Some characteristics of, and comparisons between, surface-enhanced Raman spectroscopy (SERS) and infrared reflection-absorption spectroscopy (IRRAS) for examining reactive as well as stable electrochemical adsorbates are illustrated by means of selected recent results from our laboratory. The differences in vibrational selection rules for surface Raman and infrared spectroscopy are discussed for the case of azide adsorbed on silver, and used to distinguish between "flat" and "end-on" surface orientations. Vibrational band intensity-coverage relationships are briefly considered for some other systems that are unlikely to involve coverage-induced reorientation. 

A set of SER spectra for adsorbed azide on silver, obtained for the same surface and solution conditions and for a similar sequence of electrode potentials as for the PDIR spectra in Figure 1, is shown in Figure 2. (See the figure caption and reference 7 for experimental details.) Inspection of these SER spectra in comparison with the PDIR results illustrate some characteristic differences in the information provided by the two techniques. Most prominently, in addition to the Nj" j/as band around 2060 cm"1, the former spectra exhibit three other features at lower frequencies attributable to adsorbed azide vibrations. By analogy with bulk-phase spectra for free and coordinated azide (15), the 1330 cm"1 SERS band is attributed to the N-N-N symmetric stretch, vt (2). The observation of both i/a and j/aa features in the SER spectra differs from the surface infrared results in that only the v band is obtained in the latter (2). The appearance of the vn band in SERS is of interest since this feature is symmetry forbidden in the solution azide Raman spectrum. 

Examination of the azide bending-mode region (600-700 cm 1) in the SER spectra (Figure 2) is also instructive with regard to adsorbate orientation. Thus, the pair of bands (at ca. 610 and 670 cm"1) seen at the least negative potentials are characteristic of end-on coordinated azide (15) the loss of the lower-frequency partner for E < -0.15 V is therefore also indicative of the removal of azide bound in this adsorbate geometry, again in harmony with the interpretation of the infrared spectra (7). 

Stefels J, Dijkhuizen L (1996) Characteristics of DMSP-lyase in Phaeocystis sp. (Prymnesio-phyceae). Mar Ecol Prog Ser 131 307-313... 

Rohrbaugh, W.J. andWu, E.L (1989) Factors affecting X-ray diffraction characteristics of catalyst materials. ACS Symp. Ser., 411, 279-302. 

In vitro studies with unmodified and modified N-terminal peptides of H3 demonstrated that Lys-14 acetylation did not interfere with methylation at Lys-9 by Suv39hl, while phosphorylation at Ser-10 and acetylation at Lys-9 did (Fig. 7). Further dimethylation of Lys-9 reduced enzymatic activity [186], A Suv39h double null primary mouse embryonic fibroblasts had higher levels of Ser-10 phos-phorylated H3 than wild type cells. These mutant cells had increased numbers of micro- and polynuclei. Oversized nuclei were characteristic of subpopulation of cells. The level of Lys-9 methylated FI3 in wild type cells and Suv39h double null cells was similar, demonstrating that other FI3 methyltransferases were involved [195]. Phosphorylation of Ser-10 by Ipll/aurora was also studied. Acetylation at Lys-14 promoted the activity of the mitotic kinase, while dimethylation, but not acetylation at Lys-9, reduced activity of the kinase [186]. 

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