Marker Bands Research Articles

B-PO04-148 ZERO FLOUROSCOPY WATCHMAN FLX IMPLANTATION

Standard workflow for the Watchman FLX left atrial appendage (LAA) occlusion device requires both transesophageal echocardiography(TEE) and fluoroscopy(FL). To demonstrate the Watchman FLX has unique characteristics which permit additional evolution of the implant protocol including the elimination of ionizing radiation, contrast dye, and lead aprons. Consecutive patients (n=12) were implanted with a FLX device at 2 US centers using a workflow modification to allow no FL throughout the entire procedure. To facilitate echocardiographic visualization of the moment the FLX was aligned with the tip of the Watchman Access System sheath (WAS), the standard protocol was modified. Rather than advancing only to the radiopaque marker band prior to insertion, the FLX was advanced flush to the tip, past the radiopaque marker band. Once inserted into the WAS, the deployment knob was used to advance the Watchman 2-3 mm so that the FLX was partially deployed inside the sheath. As a result, upon alignment of the FLX with the sheath's tip it was echogenic allowing confirmation without FL. TEE was then used to visualize unsheathing the FLX within the LAA. Patients were 58% male (n=7) with mean age of 78(±5), CHADS-VASC 4(±1), and HAS-BLED 3(±1). Fluoroscopy time, time in lead, and contrast use were zero. Same day discharge was successful in 67%(n=8). 67% (n=8) were taking Direct Oral Anticoagulant (DOAC) or warfarin prior to procedure and of these 88% (n=7) were uninterrupted on the day of procedure. 33% (4/12) were either on Dual Antiplatelet Therapy (DAPT) or not on any anticoagulation preoperatively and all 4 of these were discharged on DAPT. Total time in the procedure room was 67 (±22) minutes with 51(±22) minutes of anesthesia time. A single device was used in 92% (n=11). The mean LAA maximum size was 19 (±3) mm with least device compression 20% (±9). There were no complications. No patients had a peri-device leak at implant. One patient refused TEE at follow up. At follow-up imaging at least 45 days later there were no leaks >5mm with 91% (10/11) having no leak and 1 patient having a 4mm leak. Zero fluoroscopy TEE guided Watchman FLX implantation is feasible and safe with no perceptible decrease in efficiency.

Nutrients, secondary metabolites and anti-oxidant activity of Moringa oleifera leaves and Moringa-based commercial products

Moringa oleifera is a multipurpose plant with a wide range of applications. The leaves of M. oleifera (MOLs) collected from Limpopo, Mpumalanga and Gauteng provinces, as well as commercially sold Moringa-based products (MBCPs), were investigated for nutrient content, secondary metabolites profiles and antioxidant activity. Fourier Transform infrared spectroscopy provided a rapid tool for the quality assurance and authentication of MBCPs. Marker bands representing the OH stretch, aromatic group stretch (C = C), sharp absorption band (C = O) and typical aliphatic CH stretch, were observed in the MBCPs. The profiling of the methanol extract using UPLC-Q-TOF-MS revealed 19 compounds namely; flavonoids and phenolic acid derivatives identified as, Glucomoringin (1), 3-Caffeoyl quinic acid (2), 3-p-Coumaroylquinic acid (3), 4-Caffeoyl quinic acid (4), Acetyl 4-(α-l-rhamnopyranosyloxy) benzyl glucosinolate (5), Apigenin C-diglycoside (6), 4-p-Coumaroyl quinic acid (7), 4-Feruloylquinic acid (8), Quercetin-3-O-rutinoside (9), Apigenin C-hexose (10), Quercetin-7-hexose (11), Quercetin-3-hexose (12), Quercetin-3-acetyl-hexose (13), Kaempferol-3-O-rutinoside (14), Luteolin-7-O-glucoside (15), kaempferol-3-hexose (16), Cyanidin hexose (17), Isorhamnetin-hexose (18) and Kaempferol acetyl hexose (19). A strong comparability was observed between antioxidant activity and nutrient content of the leaves. Leaves from Limpopo exhibited the highest nutrient content and lowest IC50 value (19.1 ± 0.26 µg/mL) indicating satisfactory antioxidant activity, followed by leaves harvested from Mpumalanga (22.8 ± 0.60 µg/mL) and Gauteng (24.2 ± 0.21 µg/mL). Geographical location played a limited role in the secondary metabolites profiling of M. oleifera. All the leaf specimens studied contain adequate antioxidants, nutrients and therefore useful in the manufacture of food, body products, drugs and phyto-pharmaceuticals with therapeutic value.

SERS-Based Evaluation of the DNA Methylation Pattern Associated With Progression in Clonal Leukemogenesis of Down Syndrome.

Here we show that surface-enhanced Raman scattering (SERS) analysis captures the relative hypomethylation of DNA from patients with acute leukemia associated with Down syndrome (AL-DS) compared with patients diagnosed with transient leukemia associated with Down syndrome (TL-DS), an information inferred from the area under the SERS band at 1005 cm–1 attributed to 5-methycytosine. The receiver operating characteristic (ROC) analysis of the area under the SERS band at 1005 cm–1 yielded an area under the curve (AUC) of 0.77 in differentiating between the AL-DS and TL-DS groups. In addition, we showed that DNA from patients with non-DS myeloproliferative neoplasm (non-DS-MPN) is hypomethylated compared to non-DS-AL, the area under the SERS band at 1005 cm–1 yielding an AUC of 0.78 in separating between non-DS-MPN and non-DS-AL. Overall, in this study, the area of the 1005 cm–1 DNA SERS marker band shows a stepwise decrease in DNA global methylation as cells progress from a pre-leukemia to a full-blown acute leukemia, highlighting thus the potential of SERS as an emerging method of analyzing the methylation landscape of DNA in the context of leukemia genesis and progression.

SERS-based DNA methylation profiling allows the differential diagnosis of malignant lymphadenopathy

This study highlights the potential of surface-enhanced Raman scattering (SERS) to differentiate between B-cell lymphoma (BCL), T-cell lymphoma (TCL), lymph node metastasis of melanoma (Met) and control (Ctr) samples based on the specific SERS signal of DNA extracted from lymph node tissue biopsy. Differences in the methylation profiles as well as the specific interaction of malignant and non-malignant DNA with the metal nanostructure are captured in specific variations of the band at 1005 cm−1, attributed to 5-methylcytosine and the band at 730 cm−1, attributed to adenine. Thus, using the area ratio of these two SERS marker bands as input for univariate classification, an area under the curve (AUC) of 0.70 was achieved in differentiating between malignant and non-malignant DNA. In addition, DNA from the BCL and TCL groups exhibited differences in the area of the SERS band at 730 cm−1, yielding an AUC of 0.84 in differentiating between these two lymphadenopathies. Lastly, using multivariate data analysis techniques, an overall accuracy of 94.7% was achieved in the differential diagnosis between the BCL, TCL, Met and Ctr groups. These results pave the way towards the implementation of SERS as a novel tool in the clinical setting for improving the diagnosis of malignant lymphadenopathy.

Transient Near-UV Absorption of the Light-Driven Sodium Pump Krokinobacter eikastus Rhodopsin 2: A Spectroscopic Marker for Retinal Configuration.

We report a transient signature in the near-UV absorption of Krokinobacter eikastus rhodopsin 2 (KR2), which spans from the femtosecond up to the millisecond time scale. The signature rises with the all-trans to 13-cis isomerization of retinal and decays with the reisomerization to all-trans in the late photocycle, making it a promising marker band for retinal configuration. Hybrid quantum mechanics/molecular mechanics simulations show that the near-UV absorption signal corresponds to an S0 → S3 and/or an S0 → S5 transition, which is present in all photointermediates. These transitions exhibit a negligible spectral shift by the altering protein environment, in contrast to the main absorption band. This is rationalized by the extension of the transition densities that omits the Schiff base nitrogen. Further characterization and first steps into possible optogenetic applications were performed with near-UV quenching experiments of an induced photostationary state, yielding an ultrafast regeneration of the parent state of KR2.

An Engineered Biliverdin-Compatible Cyanobacteriochrome Enables a Unique Ultrafast Reversible Photoswitching Pathway

Cyanobacteriochromes (CBCRs) are promising optogenetic tools for their diverse absorption properties with a single compact cofactor-binding domain. We previously uncovered the ultrafast reversible photoswitching dynamics of a red/green photoreceptor AnPixJg2, which binds phycocyanobilin (PCB) that is unavailable in mammalian cells. Biliverdin (BV) is a mammalian cofactor with a similar structure to PCB but exhibits redder absorption. To improve the AnPixJg2 feasibility in mammalian applications, AnPixJg2_BV4 with only four mutations has been engineered to incorporate BV. Herein, we implemented femtosecond transient absorption (fs-TA) and ground state femtosecond stimulated Raman spectroscopy (GS-FSRS) to uncover transient electronic dynamics on molecular time scales and key structural motions responsible for the photoconversion of AnPixJg2_BV4 with PCB (Bpcb) and BV (Bbv) cofactors in comparison with the parent AnPixJg2 (Apcb). Bpcb adopts the same photoconversion scheme as Apcb, while BV4 mutations create a less bulky environment around the cofactor D ring that promotes a faster twist. The engineered Bbv employs a reversible clockwise/counterclockwise photoswitching that requires a two-step twist on ~5 and 35 picosecond (ps) time scales. The primary forward Pfr → Po transition displays equal amplitude weights between the two processes before reaching a conical intersection. In contrast, the primary reverse Po → Pfr transition shows a 2:1 weight ratio of the ~35 ps over 5 ps component, implying notable changes to the D-ring-twisting pathway. Moreover, we performed pre-resonance GS-FSRS and quantum calculations to identify the Bbv vibrational marker bands at ~659,797, and 1225 cm−1. These modes reveal a stronger H-bonding network around the BV cofactor A ring with BV4 mutations, corroborating the D-ring-dominant reversible photoswitching pathway in the excited state. Implementation of BV4 mutations in other PCB-binding GAF domains like AnPixJg4, AM1_1870g3, and NpF2164g5 could promote similar efficient reversible photoswitching for more directional bioimaging and optogenetic applications, and inspire other bioengineering advances.

Elucidation of the structure of supramolecular polymorphs in peptide nanofibres using Raman spectroscopy

AbstractPeptide fibre formation via molecular self‐assembly is a key step in a range of cellular processes and increasingly considered as an approach to produce supramolecular biomaterials. We previously demonstrated the self‐assembly of the tripeptide lysine‐dityrosine (KYY) as a substrate for the formation of proton‐conducting melanin‐like materials. Point based Raman scattering is one of several techniques which were used to characterise the secondary structure of the KYY nanofibre but as is often the case with this type of fibre, the spectra are rather complex and in addition there were variations in intensity between samples making interpretation difficult. Using Raman mapping we show that, as a drop of KYY in solution dries, it self‐assembles into two different fibre forms and the simpler spectra obtained for each are easier to interpret. The tyrosine amide marker bands, 852 and 828 cm−1, are present in both forms with similar intensities indicating the formation of a similar secondary structure in both forms with some stacking of the tyrosine rings. However, the tyrosine marker bands at 1614 and 1661 cm−1 vary considerably in intensity between the two forms. It is concluded that both forms consist of stacked polypeptide units joined by hydrogen bonds to form structures similar to β‐sheet structures in longer peptides. There are other clear differences such the large intensity difference in the lysine side chain band at 1330 cm−1 and the relative intensities of the bands at 982 and 1034 cm−1. These differences are attributed to changes in the conformation of tyrosine side chains causing different electron withdrawing effects on the ring.

Effects of Femtosecond UV Laser Pulses on the Structure and Surface Dynamics of Medicinal Plants DNA, Monitored by Surface-Enhanced Raman Spectroscopy

Potential medical application of UV laser pulses for cancer treatment is one of the main motivations behind this study. Surface-enhanced Raman signatures-based structural and (sub)picosecond dynamical characterization of genomic DNAs from different medicinal plants are presented. Moreover, structural and surface dynamical changes induced in genomic DNAs from selected medicinal plants species by UV femtosecond laser pulses (λ=280 nm, 170 fs) were investigated between 300 and 1800 cm−1. As a general observation, after nucleic acids irradiation some modes became higher in intensity especially in the wavenumber range between 1050 cm−1–1650 cm−1 or new profiles appeared in this interval in the surface-enhanced Raman spectroscopy (SERS) characteristics. Changes in the structure of dA, dG, dC dT residues, nucleic acid backbone and deoxyribose or unstacking of DNA bases were found. Large wavenumber shifts of the marker bands, which appear in the SERS spectra upon nucleic acids irradiation might be associated with loss of essential structural organization of DNA. As far as surface dynamics of DNA is concerned, for control nucleic acids functional groups, the global relaxation times varied between 0.39–1.77 ps and for UV femtosecond laser pulses-irradiated DNAs, this parameter was slower than 0.35 ps and faster than 1.63 ps. A decrease of the limit values of global relaxation times variation interval is to be observed upon UV treatment of nucleic acids. This faster surface dynamics might be explained by the presence of broken bonds (lesions) in DNA systems after laser pulses irradiation.

A Near-Infrared "Matchbox Size" Spectrometer to Detect and Quantify Malaria Parasitemia.

New point-of-care diagnostic approaches for malaria that are sensitive to low parasitemia, easy to use in a field setting, and affordable are urgently required to meet the World Health Organization's objective of reducing malaria cases and related life losses by 90% globally on or before 2030. In this study, an inexpensive "matchbox size" near-infrared (NIR) spectrophotometer was used for the first time to detect and quantify malaria infection in vitro from isolated dried red blood cells using a fingerpick volume of blood. This the first study to apply a miniaturized NIR device to diagnose a parasitic infection and identify marker bands indicative of malaria infection in the NIR region. An NIR device has many advantages including wavelength accuracy and repeatability, speed, resolution, and a greatly improved signal-to-noise ratio compared to existing spectroscopic options. Using multivariate data analysis, we discriminated control red blood cells from infected cells and established the limit of detection of the technique. Principal component analysis displayed a good separation between the infected and uninfected RBCs, while partial least-squares regression analysis yielded a robust parasitemia prediction with root-mean-square error of prediction values of 0.446 and 0.001% for the higher and lower parasitemia models, respectively. The R2 values of the higher and lower parasitemia models were 0.947 and 0.931, respectively. Finally, an estimated parasitemia detection limit of 0.00001% and a qunatification limit of 0.001% was achieved; to ascertain the true efficacy of the technique for point-of-care screening, clinical studies using large patient numbers are required, which is the subject of future studies.

Low DNA and high BSA binding affinity of cationic ruthenium(II) organometallic featuring pyridine and 2’-hydroxychalcone ligands

The chiral-at-metal, piano-stool ruthenium(II) racemic organometallic [Ru(cymene)(chalconato)(pyridine)]PF6 was prepared by a multistep solution synthesis and its molecular and crystal structure was determined by single crystal X-ray diffraction. The compound crystallizes in a centrosymmetric triclinic P-1 space group with two molecules of opposite chirality within the asymmetric unit. Ruthenium is embedded in an octahedral half-sandwich coordination environment with four different donors, which generates the chirality of the metal centre. The formation of the organometallic was monitored ex-situ by infrared spectroscopy. The pyridine coordination to Ru(II) was particularly analysed to find its characteristic marker bands. The complex was also characterized by elemental analysis and NMR spectroscopy in solution. Its interaction with CT DNA and bovine serum albumin (BSA) was investigated by electron spectroscopy and spectrofluorimetry. The organometallic binds to DNA predominantly by electrostatic forces with low Kb value. On the contrary, its high affinity for BSA was confirmed by strong fluorescence quenching. The synchronous emission spectra revealed that the microenvironment of tryptophan is more affected compared to the environment of tyrosine.

Identification of Five Types Kampar River Fish With Genetic Approach

Fish identification in the mainland waters of Riau Province is generally carried out based on morphological characteristics. To identify fish species accurately in a short time, the DNA Barcoding method with a molecular approach is used. Five types of fish were taken from Kampar River and coded as MJ313, PJ36, SJ35, BJ33, and GJ41. The genes of these five fish were amplified, and PCR products were sequenced and analyzed using bioinformatics software. The editing of the sequencing results and the determination of the nucleotide composition were analyzed using Mega5 software. DNA sequences were aligned using the ClustalW software. The sequences obtained are then compared with GeneBank data using Basic Local Alignment Search Tools (BLAST). The results showed that the species with the code MJ313 and GJ41 were Channa striata, PJ36 were Osteochilus hasseltii, BJ33 were Mystus sp. Based on the sample examination, the species coded SJ35 cannot be determined because the marker band is low so that it is not visible. The results of the analysis on species coded SJ35 indicate that there is no COI report for species coded SJ35 on GeneBank.

Solid-state and solution-state self-association of dimethylarsinic acid: IR, NMR and theoretical study

The structure of dimethylarsinic acid (Me2AsOOH, DMA) in crystal and in solution in aprotic medium was studied by X-ray, spectroscopic (IR, NMR and Raman) and quantum chemical calculation (DFT) methods. Two polymorphs of DMA – hydrogen-bonded cyclic dimers or infinite chains – were obtained by growing crystals from protic and aprotic solvents. By comparison of the experimental data with the results of quantum-chemical calculations performed with periodic boundary conditions we propose ways how to distinguish two polymorphs using IR marker bands. The self-association of DMA in polar aprotic solution was studied by low-temperature NMR (T = 100 K, solvent CDF3/CDF2Cl mixture). By using H/D isotope effects on 1H NMR chemical shifts (appearing after a partial deuteration of DMA in the mobile proton sites) we were able to prove that in solution DMA forms cyclic dimers with two equivalent strong hydrogen bonds (in contrast, for example, to Me2POOH acid, which forms predominantly cyclic trimers). Based on the available IR spectra, the type of complexation does not change when the aprotic solvent is varied.

A Resonance Raman Marker Band Characterizes the Slow and Fast Form of Cytochrome c Oxidase.

Cytochrome c oxidase (CcO) in its as-isolated form is known to exist in a slow and fast form, which differ drastically in their ability to bind oxygen and other ligands. While preparation methods have been established that yield either the fast or the slow form of the protein, the underlying structural differences have not been identified yet. Here, we have performed surface enhanced resonance Raman (SERR) spectroscopy of CcO immobilized on electrodes in both forms. SERR spectra obtained in resonance with the heme a3 metal-to-ligand charge transfer (MLCT) transition at 650 nm displayed a sharp vibrational band at 748 or 750 cm-1 when the protein was in its slow or fast form, respectively. DFT calculations identified the band as a mode of the His-419 ligand that is sensitive to the oxygen ligand and the protonation state of Tyr-288 within the binuclear complex. Potential-dependent SERR spectroscopy showed a redox-induced change of this band around 525 mV versus Ag/AgCl exclusively for the fast form, which coincides with the redox potential of the Tyr-O/Tyr-O- transition. Our data points to a peroxide ligand in the resting state of CcO for both forms. The observed frequencies and redox sensitivities of the Raman marker band suggest that a radical Tyr-288 is present in the fast form and a protonated Tyr-288 in the slow form.

Structural Recognition of Triple-Stranded DNA by Surface-Enhanced Raman Spectroscopy.

Direct, label-free analysis of nucleic acids via surface-enhanced Raman spectroscopy (SERS) has been continuously expanding its range of applications as an intriguing and powerful analytical tool for the structural characterization of diverse DNA structures. Still, interrogation of nucleic acid tertiary structures beyond the canonical double helix often remains challenging. In this work, we report for the first time the structural identification of DNA triplex structures. This class of nucleic acids has been attracting great interest because of their intriguing biological functions and pharmacological potential in gene therapy, and the ability for precisely engineering DNA-based functional nanomaterials. Herein, structural discrimination of the triplex structure against its duplex and tertiary strand counterparts is univocally revealed by recognizing key markers bands in the intrinsic SERS fingerprint. These vibrational features are informative of the base stacking, Hoogsteen hydrogen bonding and sugar–phosphate backbone reorganization associated with the triple helix formation. This work expands the applicability of direct SERS to nucleic acids analysis, with potential impact on fields such as sensing, biology and drug design.

Near-Infrared Spectra of High-Density Crystalline H2O Ices II, IV, V, VI, IX, and XII.

High-pressure ice polymorphs are important for our understanding of hydrogen bonding and exist in the interior of the earth and icy moons. Nonetheless, spectroscopic information about them is scarce, where no information about their optical properties in the near-infrared (NIR) region is available at all. We here report NIR spectra of six ice polymorphs differing in terms of their density and O-atom topology, namely, ices II, IV, V, VI, IX, and XII, in comparison with the known spectra of ice Ih. By contrast to earlier work, we do not use mulling agents or transmission of thin films but use diffuse reflectance on powdered samples in liquid nitrogen. The first overtone of the OH-stretching mode is identified as the marker band most suitable to distinguish between these ices. There is a clear blue shift of this band that increases with increasing topological density in addition to a significant narrowing of the band.

Transient electronic and vibrational signatures during reversible photoswitching of a cyanobacteriochrome photoreceptor

Cyanobacteriochromes (CBCRs) are an emerging class of photoreceptors that are distant relatives of the phytochromes family. Unlike phytochromes, CBCRs have gained popularity in optogenetics due to their highly diverse spectral properties spanning the UV to near-IR region and only needing a single compact binding domain. AnPixJg2 is a CBCR that can reversibly photoswitch between its red-absorbing (15ZPr) and green-absorbing (15EPg) forms of the phycocyanobilin (PCB) cofactor. To reveal primary events of photoconversion, we implemented femtosecond transient absorption spectroscopy with a homemade LED box and a miniature peristaltic pump flow cell to track transient electronic responses of the photoexcited AnPixJg2 on molecular time scales. The 525 nm laser-induced Pg-to-Pr reverse conversion exhibits a ~3 ps excited-state lifetime before reaching the conical intersection (CI) and undergoing further relaxation on the 30 ps time scale to generate a long-lived Lumi-G ground state intermediate en route to Pr. The 650 nm laser-induced Pr-to-Pg forward conversion is less efficient than reverse conversion, showing a longer-lived excited state which requires two steps with ~13 and 217 ps time constants to enter the CI region. Furthermore, using a tunable ps Raman pump with broadband Raman probe on both the Stokes and anti-Stokes sides, we collected the pre-resonance ground-state femtosecond stimulated Raman spectroscopy (GS-FSRS) data with mode assignments aided by quantum calculations. Key vibrational marker bands at ~850, 1050, 1615, and 1649 cm−1 of the Pr conformer exhibit a notable blueshift to those of the Pg conformer inside AnPixJg2, reflecting the PCB chromophore terminal D (major) and A (minor) ring twist along the primary photoswitching reaction coordinate. This integrated ultrafast spectroscopy and computational platform has the potential to elucidate photochemistry and photophysics of more CBCRs and photoactive proteins in general, providing the highly desirable mechanistic insights to facilitate the rational design of functional molecular sensors and devices.

Indirect Quantification of Glyphosate by SERS Using an Incubation Process With Hemin as the Reporter Molecule: A Contribution to Signal Amplification Mechanism.

The indirect determination of the most used herbicide worldwide, glyphosate, was achieved by the SERS technique using hemin chloride as the reporter molecule. An incubation process between hemin and glyphosate solutions was required to obtain a reproducible Raman signal on SERS substrates consisting of silicon decorated with Ag nanoparticles (Si-AgNPs). At 780 nm of excitation wavelength, SERS spectra from hemin solutions do not show extra bands in the presence of glyphosate. However, the hemin bands increase in intensity as a function of glyphosate concentration. This allows the quantification of the herbicide using as marker band the signal associated with the ring breathing mode of pyridine at 745 cm−1. The linear range was from 1 × 10−10 to 1 × 10−5 M and the limit of detection (LOD) was 9.59 × 10−12 M. This methodology was successfully applied to the quantification of the herbicide in honey. From Raman experiments with and without silver nanoparticles, it was possible to state that the hemin is the species responsible for the absorption in the absence or the presence of the herbicide via vinyl groups. Likewise, when the glyphosate concentration increases, a subtle increase occurs in the planar orientation of the vinyl group at position 2 in the porphyrin ring of hemin over the silver surface, favoring the reduction of the molecule. The total Raman signal of the hemin-glyphosate incubated solutions includes a maximized electromagnetic contribution by the use of the appropriate laser excitation, and chemical contributions related to charge transfer between silver and hemin, and from resonance properties of Raman scattering of hemin. Incubation of the reporter molecule with the analyte before the conjugation with the SERS substrate has not been explored before and could be extrapolated to other reporter-analyte systems that depend on a binding equilibrium process.

On Complex Formation between 5-Fluorouracil and β-Cyclodextrin in Solution and in the Solid State: IR Markers and Detection of Short-Lived Complexes by Diffusion NMR.

In this work, the nuclear magnetic resonance (NMR) and IR spectroscopic markers of the complexation between 5-fluorouracil (5-FU) and β-cyclodextrin (β-CD) in solid state and in aqueous solution are investigated. In the attenuated total reflectance(ATR) spectra of 5-FU/β-CD products obtained by physical mixing, kneading and co-precipitation, we have identified the two most promising marker bands that could be used to detect complex formations: the C=O and C-F stretching bands of 5-FU that experience a blue shift by ca. 8 and 2 cm−1 upon complexation. The aqueous solutions were studied by NMR spectroscopy. As routine NMR spectra did not show any signs of complexation, we have analyzed the diffusion attenuation of spin–echo signals and the dependence of the population factor of slowly diffusing components on the diffusion time (diffusion NMR of pulsed-field gradient (PFG) NMR). The analysis has revealed that, at each moment, ~60% of 5-FU molecules form a complex with β-CD and its lifetime is ca. 13.5 ms. It is likely to be an inclusion complex, judging from the independence of the diffusion coefficient of β-CD on complexation. The obtained results could be important for future attempts of finding better methods of targeted anticancer drug delivery.

Monitoring peptide tyrosine nitration by spectroscopic methods.

Oxidative stress can lead to various derivatives of the tyrosine residue in peptides and proteins. A typical product is 3-nitro-L-tyrosine residue (Nit), which can affect protein behavior during neurodegenerative processes, such as those associated with Alzheimer's and Parkinson's diseases. Surface enhanced Raman spectroscopy (SERS) is a technique with potential for detecting peptides and their metabolic products at very low concentrations. To explore the applicability to Nit, we use SERS to monitor tyrosine nitration in Met-Enkephalin, rev-Prion protein, and α-synuclein models. Useful nitration indicators were the intensity ratio of two tyrosine marker bands at 825 and 870cm-1 and a bending vibration of the nitro group. During the SERS measurement, a conversion of nitrotyrosine to azobenzene containing peptides was observed. The interpretation of the spectra has been based on density functional theory (DFT) simulations. The CAM-B3LYP and ωB97XD functionals were found to be most suitable for modeling the measured data. The secondary structure of the α-synuclein models was monitored by electronic and vibrational circular dichroism (ECD and VCD) spectroscopies and modeled by molecular dynamics (MD) simulations. The results suggest that the nitration in these peptides has a limited effect on the secondary structure, but may trigger their aggregation.

Bacterial Colonization on the Surface of Copper Sulfide Minerals Probed by Fourier Transform Infrared Micro-Spectroscopy

Biofilm formation is a molecular assembly process occurring at interfaces, such as in bioleaching processes. The real time monitoring of the marker bands of amide I/amide II by FTIR microspectroscopy during Acidithiobacillus ferrooxidans colonization on chalcopyrite surfaces revealed the central role of lipids, proteins and nucleic acids in bacterial cell attachment to copper sulfide surfaces. The Raman and FTIR spectra of the interactions of Acidithiobacillus ferrooxidans with bornite are also reported.