Pigment characterization of important golden age panel paintings of the 17th century.

Samples were obtained from two world-famous 17th century panel paintings of the Gdansk school of panting: 'Seven Acts of Charity' (1607, in St. Mary's Church in Gdansk, Poland) by Anton Möller and 'Angelic Concert' (1611, in Diocesan Museum in Pelplin, Poland) by Hermann Han. Micro-Raman spectroscopy (MRS), optical microscopy (OM), and X-ray fluorescence (XRF) spectroscopy studies of the samples were performed to characterize the pigments present in the individual painting layers (a rich palette of white, black, blue, red, and yellow pigments) and the pictorial techniques used by the artists.

Neuropeptide Y and its C-terminal fragments acting on Y2 receptor: Raman and SERS spectroscopy studies.

In this paper, we present spectroscopic studies of neuropeptide Y (NPY) and its native NPY(3-36), NPY(13-36), and NPY(22-36) and mutated acetyl-(Leu(28,31))-NPY(24-36)C-terminal fragments acting on Y2 receptor. Since there is some evidence for the correlation between the SERS patterns and the receptor binding ability, we performed a detailed analysis for these compounds at the metal/water interface using Raman spectroscopy (RS) and surface-enhanced Raman spectroscopy (SERS) methods. Many studies have suggested that interactions of this kind are crucial for a variety of biomedical and biochemical phenomena. The identification of amino acids in these peptide sequences by SERS allowed us to determine which molecular fragments were responsible for the interaction with the silver nanoparticle surface. Our findings demonstrated that in all of the investigated compounds, the NPY(32-36)C-terminal fragment (Thr(32)-Arg(33)-Gln(34)-Arg(35)-Tyr(36)NH2) was involved in the adsorption process onto metal substrate. The results of the present study suggest that the same molecular fragment interacts with the Y2 receptor, what proved the usefulness of the SERS method in the study of these biologically active compounds. The search for analogs acting on Y2 receptor may be important from the viewpoint of possible future clinical applications.

Raman, surface-enhanced Raman, and density functional theory characterization of (diphenylphosphoryl)(pyridin-2-, -3-, and -4-yl)methanol.

This work presents near-infrared Raman spectroscopy (FT-RS) and surface-enhanced Raman scattering (SERS) studies of three pyridine-α-hydroxymethyl biphenyl phosphine oxide isomers: (diphenylphosphoryl)(pyridin-2-yl)methanol (α-Py), (diphenylphosphoryl)(pyridin-3-yl)methanol (ß-Py), and (diphenylphosphoryl)(pyridin-4-yl)methanol (γ-Py) adsorbed onto colloidal and roughened in oxidation-reduction cycles silver surfaces. The molecular geometries in the equilibrium state and vibrational frequencies were calculated by density functional theory (DFT) at the B3LYP 6-311G(df,p) level of theory. The results imply that the most stable structure of the investigated molecules is a dimer created by two intermolecular hydrogen bonds between the H atom of the α-hydroxyl group (in up (HOU) or down (HOD) stereo bonds position) and the O atom of tertiary phosphine oxide (═O) of the two monomers. Comparison the FT-RS spectra with the respective SERS spectra allowed us to predict the orientation of the hydroxyphosphonate derivatives of pyridine that depends upon both the position of the substituent relative to the ring N atom (in α-, ß-, and γ-position, respectively) and the type of silver substrate.

Vibrational characterization and adsorption mode on SERS-active surfaces of guanidino-(bromophenyl)methylphosphonic acid.

This work presents adsorption geometry of [N-butyl-guanidino-(4-bromophenyl)methyl] phosphonic acid (4-BrPhG(n-But)P) on different SERS-active substrates (colloidal and specifically prepared Ag and Au roughened substrates). The adsorption mode is deduced from the SERS selection rules and several characteristic bands of the 4-BrPhG(n-But)P molecular fragments. The SERS spectra are compared to the experimental FT-Raman spectrum. In addition, the vibrational wavenumbers and PED's obtained for 4-BrPhG(n-But)P by using density functional theory methods with B3LYP/6-311++G(**) level of theory and PCM model is briefly presented.

Crystalline transition and morphology variation of polyamide 6/CaCl2 composite during the decomplexation process.

In this work, we developed a new method to prepare porous PA6 with different morphologic feature and crystalline forms via the decomplexation of PA6/CaCl2 composite. The structures and morphology of thus obtained materials were characterized by vibrational spectroscopy (FT-IR and Raman) and scanning electron microscope (SEM) method. When amorphous PA6/CaCl2 composite films were treated in water at room temperature, PA6 re-arranges into γ form. However, decomplexation of the PA6/CaCl2 composite in boiling water produces PA6 in α crystalline form. If the PA6/CaCl2 composite is soaked in methanol, part of PA6 is dissolved or swollen in methanol/metal salt solutions. As a result, a dissolve/precipitation process occurred during the decomplexation process, which led to the formation of PA6 in α crystalline form. Further investigation demonstrates that the morphologies of the porous PA6 could be adjusted by using different solvents and/or different decomplexation conditions.

Influence of substituent type and position on the adsorption mechanism of phenylboronic acids: infrared, Raman, and surface-enhanced Raman spectroscopy studies.

This paper shows systematic spectroscopic studies using Fourier-transform infrared absorption (FT-IR), Fourier-transform Raman (FT-Raman), and surface-enhanced Raman (SERS) in an aqueous silver sol of fluoro and formyl analogues of phenylboronic acids: 2-fluorophenylboronic acid (2-F-PhB(OH)2), 3-fluorophenylboronic acid (3-F-PhB(OH)2), 4-fluorophenylboronic acid (4-F-PhB(OH)2), 2-formylphenylboronic acid (2-CHO-PhB(OH)2), 3-formylphenylboronic acid (3-CHO-PhB(OH)2), and 4-formylphenylboronic acid (4-CHO-PhB(OH)2). To produce an extensive table of vibrational spectra, density functional theory (DFT) calculations with the B3LYP method at the 6-311++G(d,p) level of theory were performed for the ground state geometry of the most stable species, dimers in cis-trans conformation. On the basis of the SERS spectral profile, the adsorption modes of the phenylboronic acid isomers were proposed. The type of substituent and its position in the phenyl ring have a strong influence on the geometry of isomers on the silver nanoparticle's surface. This effect was especially evident in the case of 4-CH-PhB(OH)2, for which dearomatization of the phenyl ring took place upon adsorption.

Vibrational and theoretical studies of the structure and adsorption mode of m-nitrophenyl α-guanidinomethylphosphonic acid analogues on silver surfaces.

This work presents Fourier transform Raman (FT-Raman), Fourier transform absorption infrared (FT-IR), and surface-enhanced Raman scattering (SERS) spectroscopic investigations of three m-nitrophenyl α-guanidinomethylphonic acids, including m-NO2PhG(cHex)P, m-NO2PhG(Morf)P, and m-NO2PhG(An)P, adsorbed onto colloidal and roughened silver surfaces. The SERS spectra were deconvoluted to determine the overlapped bands from which the specific molecular orientation can be deducted. The vibrational wavenumbers are calculated through density functional theory (DFT) at the B3LYP/6-31++G** level with the Gaussian 03, Raint, GaussSum 0.8, and GAR2PED software packages. The experimental and calculated vibrational bands are compared to those from SERS for the investigated compounds adsorbed on colloidal and roughened silver surfaces. The geometry of these molecules on the SERS-active silver surfaces is deduced from the observed changes in both the intensity and width of the Raman bands in the spectra of the bound species relative to the free species.

Effect of potential on temperature-dependent SERS spectra of neuromedin B on Cu electrode.

Adsorption of decapeptide neuromedin B (NMB) on copper electrode has been investigated by in situ surface-enhanced Raman scattering (SERS) spectroelectrochemistry in the temperature interval from 12 to 72 °C at -0.600 and -1.000 V potentials. It was found that intensities of peptide bands decrease at temperatures above 30 °C with higher decrease slope at -1.000 V. Frequency of F12 mode (1004 cm(-1)) of non-surface-interactive phenylalanine residue was found to be insensitive to temperature variation at both studied electrode potentials, while frequency-temperature curves for surface-interactive groups (Amide-III, methylene) were found to be controlled by the potential. In particular, opposite frequency-temperature trends were detected for Amide-III (Am-III) mode indicating decrease in H-bonding interaction strength of amide C[double bond, length as m-dash]O and N-H groups above 38 °C for -0.600 V, and increase in H-bonding interaction strength between 12 and 72 °C for -1.000 V. Anomalous Am-III temperature-dependence of the frequency at -1.000 V was explained by temperature-induced transformation of a disordered secondary structure to a helix-like conformation. The potential-difference spectrum revealed interaction of methylene groups with Cu surface at sufficiently negative potential values because of the appearance of a soft C-H stretching band near 2825 cm(-1) and a broad band near 2904 cm(-1) assigned to vibration of a distal C-H bond of the surface-confined methylene group. Consequently, a rapid decrease in frequency of CH(2)-stretching band with temperature was observed at -1.000 V, while no essential frequency changes were detected for this mode at -0.600 V. The results show that electrode potential controls the temperature-dependence of the frequency for vibrations associated with surface-interactive molecular groups.

Investigation of adsorption mode of a novel group of N-benzylamino(boronphenyl)methylphosphonic acids using SERS.

Here, we report a systematic surface-enhanced Raman spectroscopy (SERS) study of the structures of five N-benzylamino(boronphenyl)-methylphosphonic acids: N-benzylamino-(3-boronphenyl)-S-methylphosphonic acid (m-PhS), N-benzylamino-(4-boronphenyl)-S-methylphosphonic acid (p-PhS), N-benzylamino-(2-boronphenyl)-R-methylphosphonic acid (o-PhR), N-benzylamino-(3-boronphenyl)-R-methyl-phosphonic acid (m-PhR), and N-benzylamino-(4-boronphenyl)-R-methylphosphonic acid (p-PhR) adsorbed on nanometer-sized colloidal particles (20-25 nm). For example, we showed that all of these molecules interact with the colloidal surface through a boronophenyl ring, which plane remained vertical on the surface. For p-PhS, a preferential interaction between the P=O bond and the colloidal silver surface is observed to be stronger than for the remaining compounds. The -P(OH)(2) and -B(OH)(2) fragments take part in the adsorption process. However, the B-O bond of p-PhS and p-PhR seemed to be tilted with respect to the silver surface.

Fourier transform infrared and Raman and surface-enhanced Raman spectroscopy studies of a novel group of boron analogues of aminophosphonic acids.

Five analogues of a novel group of boron derivatives of aminophosphonic acids-N-benzylamino-(3-boronphenyl)-S-methylphosphonic acid (m-PhS), N-benzylamino-(4-boronphenyl)-S-methylphosphonic acid (p-PhS), N-benzylamino-(2-boronphenyl)-R-methylphosphonic acid (o-PhR), N-benzylamino-(3-boronphenyl)-R-methylphosphonic acid (m-PhR), and N-benzylamino-(4-boronphenyl)-R-methylphosphonic acid (p-PhR)-were studied using Fourier transform infrared (FT IR), Fourier transform Raman (FT RS), and surface-enhanced Raman (SERS) spectroscopies. Analysis of obtained FT IR and FT RS spectra show that all investigated compounds in the solid state exist as dimeric species formed by an H-bonding interaction between -B(OH)(2) moieties of each monomer. In addition, comparison of the wavenumbers, intensities, and broadness of bands from the FT Raman and SERS spectra allowed information to be obtained regarding the adsorption geometry of the investigated compounds immobilized onto an electrochemically roughened silver substrate.

Vibrational characterization of L-leucine phosphonate analogues: FT-IR, FT-Raman, and SERS spectroscopy studies and DFT calculations.

This study reports the Raman (FT-Raman) and absorption infrared (FT-IR) spectra, based on calculated wavenumbers and normal modes of vibrations, of the following compounds: L-Leu-D-NH-CH(Me)-PO(3)H(2) (LI), L-Leu-NH-C(Me)(2)-PO(3)H(2) (LII), L-Leu-D-NH-CH(Et)-PO(3)H(2) (LIII), L-Leu-L-NH-CH(Et)-PO(3)H(2) (LIV), L-Leu-L-NH-CH(EtOH)-PO(3)H(2) (LV), L-Leu-NH-C(Me)(Et)-PO(3)H(2) (LVI), L-Leu-L-NH-CH(PrA)-PO(3)H(2) (LVII), L-Leu-L-NH-CH(c-Pr)-PO(3)H(2) (LVIII), L-Leu-L-NH-CH(t-Bu)-PO(3)H(2) (LIX), L-Leu-L-NH-CH(BuA)-PO(3)H(2) (LX), L-Leu-L-NH-CH(c-Bu)-PO(3)H(2) (LXI), and L-Leu-L-NH-C(Adm)-PO(3)H(2) (LXII). The equilibrium geometries and vibrational wavenumbers were calculated using density functional theory (DFT) at the B3LYP, 6-311++G** level using Gaussian 03, Raint, GaussSum 0.8, and Gar2ped software. We briefly compare and analyze the experimental and calculated vibrational wavenumbers in the range 4000-400 cm(-1). In addition, the Raman wavenumbers are compared to those from the surface-enhanced Raman scattering (SERS) spectra for the phosphono analogues of l-leucine (l-Leu) adsorbed on a colloidal silver surface in an aqueous solution. The geometries of these molecules etched on the silver surface were deduced from observed changes in both the intensity and broadness of Raman bands in the spectra of the bound versus free species. For example, LVI appears to adsorb onto the colloidal silver particles mainly through the amine group and amide bond, which assists in the adsorption process, whereas LII shows strongly enhanced SERS bands due to the rocking, twisting, and stretching vibrations of the N(amid)C(sg)(Me)(2)P fragment, suggesting that this peptide's interaction with the silver surface occurs mainly via this fragment. On the other hand, the most dominant SERS bands of LIII and LIV due to the P═O bond stretches reflect P═O···Ag complex formation.

Potential induced changes in neuromedin B adsorption on Ag, Au, and Cu electrodes monitored by surface-enhanced Raman scattering.

Surface-enhanced Raman scattering (SERS), electrochemistry, and generalized two-dimensional correlation analysis (G2DCA) methods were used to define neuromedin B (NMB) ordered superstructures on Ag, Au, and Cu electrode surfaces at different applied electrode potentials in an aqueous solution at physiological pH. The orientation of NMB and the adsorption mechanism were determined based on the analysis of enhancement, broadness, and shift in wavenumber of particular bands, which allow drawing some conclusions about NMB geometry and changes in this geometry upon change of the electrode type and applied electrode potential. The presented data demonstrated that NMB deposited onto the Ag, Au, and Cu electrode surfaces showed bands due to vibrations of the moieties that were in contact/close proximity to the electrode surfaces and thus were located on the same side of the polypeptide backbone. These included the Phe(9) and Trp(4) rings, the sulfur atom of Met(10), and the -CCN- and -C═O units of Asn(2). However, some subtle variations in the arrangement of these fragments upon changes in the applied electrode potential were distinguished. The Amide-III vibrations exhibited an electrochemical Stark effect (potential dependent frequencies) with Stark tuning slope sensitive to the electrode material. Potential-difference spectrum revealed that the imidazole ring of His(8) was bonded to the Cu electrode surface at relatively positive potentials.

Structure of monolayers formed from neurotensin and its single-site mutants: vibrational spectroscopic studies.

The human, pig, and frog neurotensins and four single-site mutants of human neurotensin (NT), having the following modifications, [Gln(4)]NT, [Trp(11)]NT, [D-Trp(11)]NT, and [D-Tyr(11)]NT, were immobilized onto an electrochemically roughened silver electrode surface in an aqueous solution. The orientation of adsorbed molecules was determined from surface-enhanced Raman scattering (SERS) measurements. A comparison was made between these structures to determine how the change upon the mutation of the neurotensin structure influences its adsorption properties. The SERS patterns were correlated with the contribution of the structural components of the aforementioned peptides to the ability to interact with the NTR1 G-protein receptor. Briefly, the SERS spectra revealed that the substitution of native amino acids in investigated peptides influenced slightly their adsorption state on an electrochemically roughened silver surface. Thus, human, pig, and frog neurotensins and [Gln(4)]NT and [D-Tyr(11)]NT tended to adsorb to the surface via the tyrosine ring, the oxygen atom of the deprotonated phenol group of Tyr(11), and the -CH(2)- unit(s), most probably of Tyr(11), Arg(9), and/or Leu(13). The observed changes in the enhancement of the deprotonated Tyr residue SERS signals indicated a further parallel orientation of a phenol-O bond with regard to the silver surface normal for pig NT, [Gln(4)]NT, and [D-Tyr(11)]NT, whereas the orientation was slightly tilted for human and frog NT. In the case of [Trp(11)]NT and [D-Trp(11)]NT, the formation of a peptide/Ag complex was confirmed by strong SERS bands involving the phenyl co-ring of Trp(11)/d-Trp(11) and -CH(2)- vibrations and the tilted and flat orientations of the two compounds with respect to the surface substrate. The spectral features were accompanied by a SERS signal caused by vibrations of the carboxyl group of C-terminal Leu(13) and the guanidine group of Arg(9). Reported changes in SERS spectra of L and D isomers were fully supported by generalized two-dimensional correlation analysis. Additionally, a combination of mutation-labeling and vibrational spectroscopy (Fourier-transform Raman and absorption infrared) was used to investigate the possible peptide conformations and environments of the tyrosine residues.

Structure and binding of specifically mutated neurotensin fragments on a silver substrate: vibrational studies.

Here, we report a systematic study showing an analogy between the activities of peptide structural component interactions with both a metal substrate and a G-protein-coupled seven-transmembrane receptor. In the present work, N-terminal fragments of human neurotensin (NT), NT(1-6), NT(1-8), and NT(1-11), and C-terminal fragments of human neurotensin, NT(8-13) and NT(9-13), as well as six specifically mutated analogues with the following modifications, Acetyl-NT(8-13), [Dab(9)]NT(8-13), [Lys(8),Lys(9)]NT(8-13), [Lys(8)-(®)-Lys(9)]NT(8-13), [Lys(9),Trp(11),Glu(12)]NT(8-13), and Boc[Lys(9),Leu(13)OMe]NT(9-13), were immobilized onto an electrochemically roughened silver electrode surface in an aqueous solution. The orientation of the adsorbed molecules and the adsorption mechanism were determined from surface-enhanced Raman scattering (SERS) spectra. A comparison was made between the structures of the mutated fragments to determine how changes in the mutation of the structure influenced the adsorption properties. The contribution of the structural components to the peptides' ability to interact with the NTR1 receptor was correlated with the SERS patterns. The SERS spectra revealed that the substitution of native amino acids in the investigated peptides slightly influenced their adsorption state on an electrochemically roughened silver surface. Thus, all of the investigated peptides, excluding [Lys(9),Trp(11),Glu(12)]NT(8-13), tended to adsorb to the surface mainly via the oxygen atom of the deprotonated phenol group, and the phenyl ring became rearranged in a slightly different edge-on manner (NT(1-8), NT(1-11), NT(8-13), Acetyl-NT(8-13), [Dab(9)]NT(8-13), [Lys(8),Lys(9)]NT(8-13), [Lys(8)-(®)-Lys(9)]NT(8-13), NT(9-13), and Boc[Lys(9), Leu(13)OMe]NT(9-13)) or in an almost horizontal manner (N(1-6)) of the tyrosine residue. Meanwhile, [Lys(9),Trp(11),Glu(12)]NT(8-13) bound to this substrate through the tilted phenyl coring of the tryptophan residue. Small changes in the enhancement of the CCNH(2), COO(-), and -CONH- group modes upon adsorption, which were consistent with the adsorption of these peptides, also occurred (with slightly different strengths) through the nitrogen and oxygen lone pair of electrons in these groups. However, for NT(1-8), a greater preferential interaction between the guanidine group of Arg(8) and the roughened silver substrate was observed in comparison to that between the guanidine moiety of the other investigated peptides and the substrate. Vibrational spectroscopy was also used to produce an extensive table of Raman and absorption infrared spectra to allow for a rapid and accurate structural determination of these biomolecules and to allow the reader to easily follow the proposed SERS assignments.

Neuromedin C: potential-dependent surface-enhanced Raman spectra in the far-red spectral region on silver, gold, and copper surfaces.

Neuromedin C (NMC) is a decapeptide (Gly-Asn-His-Trp-Ala-Val-Gly-His-Leu-Met-NH(2)) that acts as a growth factor in a wide range of tumors including carcinomas of the pancreas, stomach, breast, prostate, and colon. We report surface-enhanced Raman spectra (SERS) of NMC on electrochemically roughened Ag, Au, and Cu electrode surfaces over an electrode potential range varying from +0.200 to -1.200 V (depending on the electrode material). We compared the SERS spectra to the Raman spectrum of the corresponding solid species. The SERS spectra were dominated by L-tryptophan (Trp) vibrations. This indicates that Trp interacted with the metallic surfaces of the electrodes, either by binding directly to the surface or by staying in close proximity to the surface. Characteristic SERS bands showed that, in the case of the Ag electrode, the Trp residue was almost perpendicular to the surface. In contrast, the Trp residue was slightly tilted with respect to the Au electrode surface, and Trp remained some distance from the surface of the Cu electrode. These differences were due to differences in surface rheology and in the type of metal (Ag vs Au vs Cu) responsible for the observed enhancement mechanism. On the other hand, variations in the electrode potentials only had a slight influence on the SERS patterns and the observed changes were mainly due to the reorientation of the Trp ring with respect to the electrode surface. These findings were fully supported by generalized two-dimensional correlation analysis (G2DCA).

Potential-dependent studies on the interaction between phenylalanine-substituted bombesin fragments and roughened Ag, Au, and Cu electrode surfaces.

In this work, we report systematic surface-enhanced Raman spectroscopy (SERS) and generalized two-dimensional correlation analysis (G2DCA) studies of the structures of five specifically modified phenylalanine-substituted C-terminal bombesin 6-14 fragments (BN(6-14)). The fragments studied have all been tested as chemotherapeutic agents in cancer therapy, and they form amino acid sequences in bombesin: cyclo[d-Phe(6),His(7),Leu(14)]BN(6-14), [D-Phe(6),Leu-NHEt(13),des-Met(14)]BN(6-14), [D-Phe(6),Leu(13)-((R))-p-Cl-Phe(14)]BN(6-14), [D-Phe(6),beta-Ala(11),Phe(13),Nle(14)]BN(6-14), and [D-Tyr(6),beta-Ala(11),Phe(13),Nle(14)]BN(6-14). We adsorbed these fragments onto roughened Ag, Au, and Cu electrode surfaces, using a potential range from -1.200 to 0.400 V, at physiological pH. We compared the adsorption mechanism of each fragment on these substrates, as well any changes observed with varying electrode potential, to determine the relationship between adsorption strength and geometry of each of the peptides wherever it was possible. For example, we showed that none of these fragments directly interact with the Ag, Au, and Cu surfaces via residues of Phe (phenylalanine) and Trp(8) (L-tryptophane at position 8 of the BN amino acid sequence) or by an amide bond, due to a very small shift in wavenumber of their characteristic vibrations. Specific interactions were recognized from the broadening, wavenumber shift, and increase in intensity of the W18 Trp(8) mode near 759 cm(-1) and decrease in nu(12) vibration frequency of the Phe residue. In general, more intense SERS bands were observed due to the Phe ring, compared with the Trp(8) ring, which suggested a preferential adsorption of phenylalanine over tryptophane. For [D-Tyr(6),beta-Ala(11),Phe(13),Nle(14)]BN(6-14), the data also suggest some interaction of a D-Tyr(6) residue (D-tyrosine at position 6). Finally, only slight rearrangements of these moieties on the substrates are observed with changes in electrode potential.

Vibrations and reorientations of H2O molecules and NO3(-) anions in [Ca(H2O)4](NO3)2 studied by incoherent inelastic neutron scattering, Raman light scattering, and infrared absorption spectroscopy.

The vibrational and reorientational motions of H(2)O ligands and NO(3)(-) anions were investigated by Fourier transform middle-infrared Raman scattering (RS) spectroscopy and phonon density of states, calculated from incoherent inelastic neutron scattering, in the high- and low-temperature phases of [Ca(H(2)O)(4)](NO(3))(2). The theoretical IR and RS spectra were also calculated by means of the quantum chemistry method using density functional theory with PBE1PBE functional at 6-311++G(2d,2p) basis set level. The temperature dependences of the full width at half maximum values of nu(s)(H(2)O) bands in both the infrared absorption and the RS spectroscopy suggest that the observed phase transitions (at T(C1) and T(C2)) are not connected with a drastic change in the speed of H(2)O reorientational motions. However, similar Raman nu(4)(NO(3)(-)) band shape measurements as a function of temperature revealed the existence of a fast NO(3)(-) reorientation in phase I, which is abruptly slowed at the phase transition at T(C1). Activation energy values for the reorientational motions of H(2)O ligands and NO(3)(-) anions were calculated.

Adsorbed States of phosphonate derivatives of N-heterocyclic aromatic compounds, imidazole, thiazole, and pyridine on colloidal silver: comparison with a silver electrode.

Here, we report a systematic surface-enhanced Raman spectroscopy (SERS) study of the structures of phosphonate derivatives of the N-heterocyclic aromatic compounds imidazole (ImMeP ([hydroxy(1H-imidazol-5-yl)methyl]phosphonic acid) and (ImMe)(2)P (bis[hydroxy-(1H-imidazol-4-yl)-methyl]phosphinic acid)), thiazole (BAThMeP (butylaminothiazol-2-yl-methyl)phosphonic acid) and BzAThMeP (benzylaminothiazol-2-yl-methyl)phosphonic acid)), and pyridine ((PyMe)(2)P (bis[(hydroxypyridin-3-yl-methyl)]phosphinic acid)) adsorbed on nanometer-sized colloidal particles. We compared these structures to those on a roughened silver electrode surface to determine the relationship between the adsorption strength and the geometry. For example, we showed that all of these biomolecules interact with the colloidal surface through aromatic rings. However, for BzAThMeP, a preferential interaction between the benzene ring and the colloidal silver surface is observed more so than that between the thiazole ring and this substrate. The PC(OH)C fragment does not take part in the adsorption process, and the phosphonate moiety of ImMeP and (ImMe)(2)P, being removed from the surface, only assists in this process.

Structural features of the adenosine conjugate in means of vibrational spectroscopy and DFT.

Vibrational spectra of adenosine bearing benzo-15-crown ether moiety [N(6)-4'-(benzo-15-crown-5)-adenosine, AC] have been recorded in solid phase (FT-IR, FT-Raman) and in aqueous solution on the silver colloid surface (SERS). To interpret a very complex vibrational pattern of experimental data, geometrical parameters (molecular structure) as well as harmonic frequencies of the isolated molecule were calculated at the density functional theory level [B3LYP/6-31G(d)]. Assignment of the observed vibrational modes is discussed on the basis of the theoretical results obtained for N(6)-4'-(benzo-15-crown-5)-adenosine as well as its molecular isolated fragments, i.e. adenosine and benzo-15-crown ether. Our analysis of SERS spectrum indicates that adenine and benzo-15-crown ether take tilted orientation while the imino group and ribose adopt almost vertical position in respect to the metal surface. Moreover, calculated atomic charge distribution gives interesting insights into changes of electron density allocation in investigated fragments.

The orientation of BN-related peptides adsorbed on SERS-active silver nanoparticles: comparison with a silver electrode surface.

We used surface-enhanced Raman scattering (SERS) to characterize the adsorption behavior of bombesin (BN) and five BN-related peptides, including phyllolitorin, [Leu(8)]phyllolitorin, neuromedin C (NMC), neuromedin B (NMB), and PG-L (Pseudophryne guntheri), in a silver colloidal solution. Our experiments show that the pyrrole coring of the Trp and aromatic ring of Phe of these peptides are preferentially adsorbed on silver nanoparticles. However, the geometry of the rings and the strength of the interactions with this surface vary among peptides. Additionally, these peptides are weakly coordinated to the colloidal silver surface through the CO fragment of a peptide bond, between Gln/Leu/His and Trp residues, and CNC and SC fragments. Also, using the recently reported SERS spectra of these peptides immobilized onto an electrochemically roughened silver electrode surface, we demonstrate substrate-induced changes in the adsorption behavior of these peptides. Comparative analysis indicates that the interactions between peptides and the enhancing surfaces depend strongly on the geometry of the Trp, CONH, and SC fragments of these biomolecules etched on the surfaces.