Polarization-sensitive resonance CSRS of deoxy-and oxyhaemoglobin

Polarization-sensitive coherent Stokes Raman scattering (CSRS) measurements of oxy- and deoxyhaemoglobin in aqueous solutions are reported. The excitation wavelengths used were chosen in the region of the Q absorption bands to achieve twofold electronic resonance. The dispersion profiles of all independent susceptibility (3) components and purely anisotropic and anti-symmetric scattering contributions were resolved within the frequency non-degenerate CSRS scheme. Eight bands of oxyhaemoglobin and five bands of deoxyhaemoglobin were observed in the range 1500-1680 cm-1. Simultaneously fitting sets of polarization spectra provided vibrational parameters (positions, bandwidths, amplitudes, phases and CSRS depolarization ratios) for each compound. Major bands were assigned to the non-totally symmetric v10, v11 and v19 modes of the porphyrin macrocycle. The phases calculated exhibited a correlation with the symmetry of the vibrations. On the basis of the spectral fits, the three additional peaks arising in the oxyhaemoglobin spectra could be ascribed to the bands of intermediate deoxyhaemoglobin. The occurrence is due to the partial photolysis of oxyhaemoglobin. Vibrational parameters of these bands were found to be essentially similar to the parameters of the bands observed in the spectra of the stable deoxyhaemoglobin. Despite the asymmetric character predicted, the major bands were all contributed to by a considerable isotropic component. A decrease in the depolarization ratio PR1212 of the anomalously polarized v19 mode from 7.7 in oxyhaemoglobin to 4.3 in deoxyhaemoglobin was observed. Such a decrease in anti-symmetric character of the vibration on release of the ligand supports the occurrence of deformation of the haem ring system

Secondary structure of bovine albumin as studied by polarization-sensitive multiplex CARS spectroscopy

The first application of polarization-sensitive multiplex coherent anti-Stokes Raman spectroscopy (MCARS) in the absence of resonance enhancement to the resolution of the secondary structure of a protein in solution is reported. Polarization MCARS spectra of bovine albumin in D2O were obtained in the range 1370 to 1730 cm−1 with the aid of the background suppression technique. The spectra were fitted simultaneously with a single set of parameters (band positions, bandwidths, amplitudes, and depolarization ratios). Polarized Raman spectra simulated with these parameters revealed a good correspondence with the spontaneous Raman spectra measured. The broad amide I′ band was decomposed assuming the three major secondary conformations of protein, of which the contribution of β-sheet structure was found to be negligible. Relative weights of α-helix and random coil conformations agree well with the estimates obtained with Raman and circular dichroism (CD) spectroscopies

The Prevalence of Titanium Dioxide Particles in Synovial Fluid Samples Drops after European Union Ban

Due to health concerns, the European Union has banned the use of titanium dioxide nanoparticles in consumables in February 2022, with a 6-month transitional period ending in August 2022. We studied the prevalence of titanium dioxide nanoparticles in synovial fluid samples during and after the transitional period. A total of 302 samples were collected as a consecutive series between 1 April 2022 and 15 June 2023 from patients visiting the department of rheumatology at VieCuri Medical Centre in Venlo, The Netherlands. The samples were primarily collected for diagnostic purposes and only clinical waste material was used for this study. From each sample, up to 40 μl of fluid was analysed with Raman spectroscopy for the presence of titanium dioxide particles. The trend in prevalence was calculated with a 3-month wide moving average. A total of 13 out of 302 samples (4.3%) contained titanium dioxide (TiO2). The prevalence of TiO2 decreased between the transitional period and the period after the ban (p = 0.0154, with a relative risk ratio of 4.9 (95% CI 1.35–17.74). There was no significant difference in patient characteristics between the TiO2 positive and the TiO2 negative group. These results are hinting towards a possible relationship between the EU-ban and the identified decrease in prevalence

Niet-lineaire vibratie spectroscopiën van biomoleculaire systemen

Er is recent veel vooruitgang geboekt in de ontwikkeling van niet-lineaire vibratie spectroscopische methoden voor onderzoek van biologische macromoleculaire systemen(1,2,3,4). De niet lineaire vibratie spectroscopische technieken die in onze groep in gebruik en in ontwikkeling zijn, zijn CARS (coherente anti-Stokes Raman verstrooiing), stRg (gestimuleerde Raman verstrooiing), IR/V-SFG (infrarood-zichtbaar licht som frequentie generatie). Daarnaast wordt gebruik gemaakt van niet-lineaire optische eigenschappen van materie, zoals parametrische fluorescentie, verschil frequentie generatie en tweede harmonische generatie, om laser emissie met geschikte karakteristieken te genereren. Als standaard techniek zijn in de groep zeer geavanceerde Raman microspectrometers voor spontane Raman verstrooiing (spR) beschikbaar. Het doel van het onderzoek is om gevoelige methoden te ontwikkelen voor detectie van kleine aantallen molekulen, bijvoorbeeld aan oppevlakken en in biologische cellen. We richten ons op de vibratie selectieve technieken omdat: 1) vibraties niet alleen geschikt zijn voor detectie maar ook voor identificatie, 2) vibraties zijn gevoelig voor inter- en intramolekulaire interacties, 3) vibraties kunnen helpen bij het bepalen van de molekulaire orientatie of de relatieve orientatie van molekulen en 4) vibraties maken het mogelijk om zeer snelle dynamica in materie te bestuderen. In het bijzonder niet-lineaire optische technieken zijn interessant vanwege: a) spectrale scheiding tussen fluorescentie en signaal (bijvoorbeeld in CARS en IR/V-SFG), b) gecollimeerde signaal bundel maakt efficiente signaal collectie mogelijk, c) hoge signaal niveaus door gebruik te maken van gestimuleerde verstrooiings processen (CARS, stRg) en/of door resonantie (IR/V-SFG), d) efficiente belichting door gecollimeerde lichtbundels, waardoor combinaties met golfgeleiders mogelijk zijn (CARS, stRg en spR) en oppervlakte gevoeligheid ontstaat door evanescente veld excitatie of intrinsieke eigenschappen van c(2) (IR/V-SFG).\ud Na een korte inleiding worden in het vervolg resultaten gepresenteerd van polarisatiegevoelige multiplex CARS, golfgeleider Raman verstrooiing en een optisch parametrische oscillator. Deze vormt het hart van een IR/V-SFG spectrometer die in ontwikkeling is

Ultrasensitive Detection and in Situ Imaging of Analytes on Graphene Oxide Analogues Using Enhanced Raman Spectroscopy

[Image: see text] We demonstrate how algorithm-improved confocal Raman microscopy (ai-CRM), in combination with chemical enhancement by two-dimensional substrates, can be used as an ultrasensitive detection method for rhodamine (R6G) molecules adsorbed from aqueous solutions. After developing a protocol for laser-induced reduction of graphene oxide, followed by noninvasive Raman imaging, a limit of detection (LOD) of 5 × 10(–10) M R6G was achieved using ai-CRM. An equivalent subnanomolar LOD was also achieved on another graphene oxide analogue −UV/ozone-oxidized graphene. These record-breaking detection capabilities also enabled us to study the adsorption kinetics and image the spatial distribution of the adsorbed R6G. These findings indicate a strong potential for algorithm-improved graphene-enhanced Raman spectroscopy as a facile method for detecting, imaging, and quantifying trace amounts of adsorbing molecules on a variety of 2D substrates

Intermolecular interaction of photoexcited Cu(TMpy-P4) with water studied by transient resonance Raman and picosecond absorption spectroscopies

photoinduced complex between Cu(TMpy-P4) and water molecules, reversibly axially coordinated to the central metal, was observed in picosecond transient absorption and nanosecond resonance Raman experiments. This complex is rapidly created (τ1 = 15 ± 5 ps) in the excited triplet (π, π*) state of Cu-porphyrin, and the subsequent relaxation is proposed to proceed via two parallel pathways. One is fast and efficient (≥90% of molecules), and presumably involves a (π, d) charge-transfer state. The second pathway is slow (τ2 >> 1 ns), has a low quantum yield (≤10%) and involves the excited (d, d) state which is responsible for transient Raman features at ≈ 1553 cm−1 (ν2*) and ≈ 1347 cm−1 (ν4*), and for low-intensity long-lived transient absorption features