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PubMed2001

Characterization of the solid-state: spectroscopic techniques.

The physical characterization of pharmaceutical solids is an integral aspect of the drug development process. This review summarizes the use of solid-state spectroscopy techniques used in the physical characterization of the active pharmaceutical ingredient, excipients, physical mixtures, and the final dosage form. A brief introduction to infrared, Raman, and solid-state NMR experimental techniques are described as well as a more thorough description of qualitative and quantitative applications. The use of solid-state imaging techniques such as IR, Raman, and TOF-SIMS is also introduced to the reader.

Chemistry, Pharmaceutical↗
PubMed1997

Quantitative FT-Raman analysis of two crystal forms of a pharmaceutical compound.

A pharmaceutical active compound H appears in two polymorphs, A and B, that are stable below and above room temperature, respectively. The A- and B-forms were found to have distinct FT-Raman spectra, in particular for a band at 1716 cm-1 (A-form) or 1724 cm-1 (B-form). Mixtures of A- in B-form were prepared, and the relative intensity of the characteristic bands at 1716 and 1724 cm-1 was found to be proportional to the relative amounts of A- and B-form in the mixtures. A calibration was made which was linear in the range from 1.8 to 15.4% (w/w) of A- in B-form. The results were compared with other methods for analysis of polymorphs: FT-IR spectrometry, differential scanning calorimetry, and powder X-ray diffractometry. A novel FT-Raman sample presentation method for inhomogeneous samples is presented.

Calorimetry, Differential Scanning↗
PubMed2003

Raman spectroscopy of selected lead minerals of environmental significance.

The Raman spectra of the minerals cerrusite (PbCO(3)), hydrocerrusite (Pb(2)(OH)(2)CO(3)), phosgenite (Pb(2)CO(3)Cl(2)) and laurionite (Pb(OH)Cl) have been used to qualitatively determine their presence. Laurionite and hydrocerrusite have characteristic hydroxyl stretching bands at 3506 and 3576 cm(-1). Laurionite is also characterised by broad low intensity bands centred at 730 and 595 cm(-1) attributed to hydroxyl deformation vibrations. The minerals cerrusite, hydrocerrusite and phosgenite have characteristic CO (nu(1)) symmetric stretching bands observed at 1061, 1054 and 1053 cm(-1). Phosgenite displays complexity in the CO (nu(3)) antisymmetric stretching region with bands observed at 1384, 1327 and 1304 cm(-1). Cerrusite shows bands at 1477, 1424, 1376 and 1360 cm(-1). The hydrocerrusite Raman spectrum has bands at slightly different positions from cerrusite, with bands at 1479, 1420, 1378 and 1365 cm(-1). The complexity of the nu(3) region is also reflected in the nu(2) and nu(4) regions with the observation of multiple bands. Laurionite is characterised by two intense bands at 328 and 272 cm(-1) attributed to PbO and PbCl stretching bands. Importantly, all four minerals are characterized by their Raman spectra, enabling the mineral identification in leachates and contaminants of environmental significance.

Environmental Pollutants↗
PubMed2000

Vibrational spectra of 3,5-dimethylpyrazole and deuterated derivatives.

The infrared (IR) and Raman spectra of 3,5-dimethylpyrazole have been recorded in the vapor, liquid (melt and solution) and solid states. Two deuterated derivatives, C5H7N-ND and C5D7N-NH, were also studied in solid state and in solutions. Instrumental resolution was relatively low, 2.0 cm(-1) in the IR and approximately 2.7 cm(-1) in the Raman spectra. The solids are made of cyclic hydrogen-bonded trimers. These trimers, present also in chloroform and acetone solutions, give rise to characteristic high absorption IR spectra in the 3200-2500 cm(-1) region, related to Fermi resonance involving nu(NH) vibrations. Bands from trimers are not present in water solutions but these solutions show spectral features similar in several ways to those of the trimer, attributable to solvent-bonded complexes. Evidence of H-bonding interactions with the other solvents is also visible in the high-frequency region. The two very intense bands in the Raman spectra of the solids appearing at 115 and 82 cm(-1) in the parent compound are also connected with a trimer formation. To interpret the experimental data, ab initio computations of the harmonic vibrational frequencies and IR and Raman intensities were carried out using the Gaussian 94 program package after full optimization at the RHF/6-31G* level for the three monomeric compounds as well as for three models of the trimer, with C3h, C3 and C1 symmetry. The combined use of experiments and computations allow a firm assignment of most of the observed bands for all the systems. In general, the agreement between theory and experiment is very good, with the exception of the IR and Raman intensities of some transitions. Particularly noticeable is the failure of the theoretical calculation in accounting for the high intensity of the Raman bands of the solid about 115 and 82 cm(-1).

Deuterium↗
PubMed1991

Internal intensity standards for heme protein UV resonance Raman studies: excitation profiles of cacodylic acid and sodium selenate.

We examine the utility of SO4(2-), ClO4-, cacodylic acid, and SeO4(2-) as internal intensity standards for Raman spectral measurements of protein structure. We find that 0.1 M SO4(2-) and ClO4- perturb the protein tertiary structure of aquomethemoglobin (met-Hb) and its fluoride (met-HbF) and azide (met-HbN3) complexes. Changes occur for the tryptophan near-UV absorption bands, the iron spin state is altered, and the fluoride ligand affinity decreases. Concentrations of ClO4- and SO4(2-) as low as 0.1 M suppress the met-HbF quaternary R----T transition induced by the allosteric effector inositol hexaphosphate (IHP). In contrast, similar concentrations of cacodylic acid and SeO4(2-) show little effect on the hemoglobin tertiary or quaternary protein structures or upon the R----T transition induced by IHP. We measure the Raman cross sections of cacodylic acid and SeO4(2-) between 218 and 514.5 nm and find that for UV excitation they are ca. 5-fold larger than ClO4- or SO4(2-). Thus, cacodylic acid and selenate can be used at lower concentrations. Cacodylic acid and SeO4(2-) are superior Raman internal intensity standards for protein structural studies.

Cacodylic Acid↗
PubMed1980

Resonance Raman spectra of flavin derivatives containing chemical modifications in positions 7 and 8 of the isoalloxazine ring.

The resonance Raman spectra of riboflavin, 7,8-dichlororiboflavin, 8-chlororiboflavin, 8-bromoriboflavin, 8-(methylmercapto)riboflavin, 7-chlorolumiflavin, 8-norlumiflavin, 7,8-norlumiflavin, and 3-CH2COOH-lumiflavin were measured in complex with riboflavin binding protein, which was used as a fluorescence quenching agent. Shifts in the positions of Raman bands in the vicinity of 1250, 1405, 1550, and 1585 cm-1 were observed in the spectra of many of these flavin derivatives. Comparable shifts were found in the IR spectra (solid KBr) of the uncomplexed flavins. The perturbed bands have been previously assigned to reasonably localized stretching modes in the isoalloxazine system, which are well removed from the 7 and 8 positions. Thus, a direct effect on these bands due to modification of the substitutents at positions 7 and 8 is precluded. These observations have led us to conclude that these Raman bands are associated with highly delocalized aromatic framework vibrations.

Carrier Proteins↗
PubMed2006

Discrimination of irradiated starch gels using FT-Raman spectroscopy and chemometrics.

The effects of gamma-irradiation on starch gels were characterized at the molecular level by Fourier transform (FT) Raman spectroscopy. Starches from five different sources were gelatinized and irradiated at 3, 5, and 10 kGy using a Co60 gamma-irradiator. Gamma-irradiation effects on starch gels were noted by the C-H stretch (2800-3000 cm(-1)) and O-H stretch (3000-3600 cm(-1)) and bend (1600-1800 cm(-1)) regions of the FT-Raman spectra. FT-Raman molecular fingerprints obtained through spectral analyses were used for discrimination of the gels based on the extent of irradiation by means of two different pattern-recognition techniques: canonical variate analysis (CVA) and soft modeling of class analogy (SIMCA). A complete discrimination of irradiated starches was attained using a hybrid partial least-squares (PLS) and CVA model, using the spectral variations in the C-H stretch and O-H stretch and bend regions of FT-Raman spectra. Using the same spectral regions, SIMCA predicted 84% of samples correctly.

Chemical Phenomena↗
PubMed2004

Raman spectroscopy of endoliths from Antarctic cold desert environments.

Six endolithic communities from Antarctic cold desert environments have been analysed by Raman spectroscopy. The extreme conditions that the organisms have to withstand in cold environments leads to the adoption of different survival strategies and adaptation of the geological environment. Production of radiation- and desiccation-protective biomolecules is identifiable but the displacement of potentially protective minerals onto the rock surface has also been detected as a protective mechanism against UV-radiation. In this work, Raman spectroscopy is demonstrated as a valuable technique to determine the organic and inorganic compounds used by microorganisms as protective mechanisms against extreme stress conditions. The data from this study will be useful for construction of molecular recognition biomarkers and remote Raman spectral sensing experiments proposed for terrestrial extremophiles in stressed environments.

Antarctic Regions↗
PubMed2006

Temperature-jump apparatus with Raman detection based on a solid-state tunable (1.80-2.05 microm) kHz optical parametric oscillator laser.

The operating characteristics of a pulsed (10 ns) tunable near-infrared (NIR) laser source are described for temperature-jump (T-jump) applications. A Q-switched Nd:YLF laser (approximately 10 ns pulses) with a 1 kHz repetition rate is used to pump a potassium titanyl arsenate (KTA) crystal-based optical parametric oscillator (OPO), producing approximately 1 mJ NIR pulses that are tunable (1.80-2.05 microm) across the 1.9 microm vibrational overtone band of water. This T-jump source has been coupled to a deep ultraviolet (UV) probe laser for Raman studies of protein dynamics. T-jumps of up to 30 degrees C, as measured via the O-H stretching Raman band of water, are readily achieved. Application to cytochrome c unfolding is demonstrated.

Animals↗
PubMed2006

Fluorescence-suppressed Raman technique for quantitative analysis of protein solution using a micro-Raman probe, the shifted excitation method, and partial least squares regression analysis.

A practical Raman analyzing technique with suppression of the strong fluorescent background in order to obtain quantitative information is proposed in the present study. The technique is based on the shifted excitation method and partial least squares regression (PLSR) analysis. The Raman system consists of a single Raman spectrometer, a background-free electrically tunable Ti:Sapphire laser (BF-ETL), and a micro-Raman probe (MRP). The system allows one to obtain reliable shifted excitation Raman spectra with a simple operation. The PLSR analysis successfully provides quantitative information from the obtained spectra with the suppression of random noise including photon shot noise. The present study demonstrates that the technique is effective for extracting quantitative information concealed behind a fluorescent background that is more than 200 times stronger than the Raman signal.

Animals↗
PubMedDate not supplied

Oncologic applications of biophotonics: prospects and problems.

The understanding of various intrinsic photobiophysical processes has prompted researchers to develop different types of biodevices for health care. In the recent past, because of extensive contributions from various groups in the field of biophotonics, several important biomedical applications are emerging in the fields of both diagnostics and therapy. In this brief review, we discuss a few specific applications related to early detection and characterization of premalignant and malignant lesions using optical spectroscopic techniques, namely, fluorescence and Raman, and in management of cancer, the emerging scene of photodynamic therapy.

Humans↗
PubMed2004

Near-field optics and spectroscopy for molecular nano-imaging.

Application of near-field optical microscopy with a sharp metallic probe to Raman spectroscopy brings microanalysis of materials to their nano-identification and imaging. The local plasmon polariton excitation on the probe tip results in the localization and amplification of the optical field at the vicinity of the tip. The tip-enhanced near-field Raman spectroscopy has analyzed DNA base molecules and single-walled carbon nanotubes (SWNTs) with the nanometric spatial resolution and sufficient sensitivity. Combined with tip pressurization and nonlinear effects, the tip-enhanced near-field Raman spectroscopy gives additional spectral information or improves the spatial resolution and sensitivity. This article introduces the recent progresses on the tip-enhanced near-field Raman spectroscopy and imaging.

Adenine↗
PubMed1998

[Discrimination of black inks by FT-Raman spectrometry].

Six brands of black inks on paper were examined by FT-Raman spectrometry. The results showed that the black inks could be discriminated by FT-Raman spectrometry. As the method is easy, quick and undestructive to samples, it is useful in black ink examination.

Forensic Medicine↗
PubMed2003

Characterization of condom lubricant components using Raman spectroscopy and Raman chemical imaging.

A condom can be described as a protective sheath used as a contraceptive or to protect against sexually transmitted diseases. However, individuals also use condoms during the commission of sexual assaults to prevent identification through deposited biological material. Raman spectroscopy offers a novel approach to identifying the presence of condom lubricant components. Furthermore, Raman chemical imaging expands on conventional Raman spectroscopy to characterize multiple condom lubricant components simultaneously in a manner that effectively demonstrates heterogeneous sample mixtures both spectrally and spatially. Known reference materials, liquid and solid lubricant components of common condom brands were successfully characterized using Raman dispersive spectroscopy and Raman chemical imaging without extensive sample preparation inherent to other analytical methods. The characterization of these materials demonstrates the potential of this technique to become a routine screening method for condom lubricants. This preliminary investigation provides a basis for future studies to determine the feasibility of Raman spectroscopy and Raman chemical imaging for condom lubricant trace detection in case type samples.

Condoms↗
PubMed1992

Fourier transform infrared/Raman differentiation and characterization of cis- and trans-2,5-dimethoxy-4,beta-dimethyl-beta-nitrostyrenes: precursors to the street drug STP.

Fourier transform Raman and infrared spectra of pure cis(Z)- and trans(E)-2,5-dimethoxy-4,beta-dimethyl-beta-nitrostyrene (precursors of the psychotomimetic street drug STP or DOM) were recorded in the solid state. The spectra show characteristic features of the ethylene moiety and of the aryl and nitro substituents which permit ready differentiation and identification of these isomers. A very strong Raman line at 1670 cm-1 from the cis isomer for the C=C stretching mode, in comparison with a strong Raman line at 1641 cm-1 for the trans isomer, affords primary differentiation of these substances. A second characteristic, of both the Raman and infrared (IR) spectra, is that the frequency of the strong symmetric nitro (NO2) stretching band is about 40 cm-1 higher in the cis (1346 cm-1) than the trans isomer (1301 cm-1). All major IR and Raman bands are reported and given vibrational assignments.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed2005

[Influence of strain in the Si cap layer of Si/SiGe heterostructure on its Raman spectra].

Strained Si/SiGe heterostructure was prepared by high dose Ge ion implantation and a subsequent high temperature rapid thermal processing method. A 325 nm UV laser was used to analyze the Raman spectra of the strained Si cap layer. It was found that tensile strain in the Si cap layer can induce a shift toward lower frequency of the first order Raman scattering peak of 520 cm(-1). In light of the variation of peak position, a lateral tensile stress of 12.5 x 10(8) N x m(-2) in Si cap layer was worked out. However, the tensile strain in the Si cap layer can not lead to a variation of the sub-order Raman scattering peaks around 1 555 and 2 330 cm(-1).

Algorithms↗
PubMed2006

[FT-Raman spectroscopic investigation on hypothyroid cancer].

The normal and malignant tissues from hypothyroid were investigated by FT-Raman spectroscopy. The results show that two characteristic Raman spectral peaks of normal tissues appeared at 503 and 758 cm(-1) (corresponding to theextension vibration of C--I band and the vibration of benzene rings respectively) in the range of 400-3500 cm(-1). The two peaks disappeared at malignant tissues. The intensity of the characteristic vibration peaks of normal tissues appearing at 3 062 and 1 003 cm(-1) corresponding to tyrosine weakened in malignant tissues. Thus, FT-Raman spectroscopy is a potential method in the diagnosis of hypothyroid cancer.

Humans↗