Biomedical subjects

Janina Kneipp

Publications and source records attributed to Janina Kneipp.

9 recordsLinked to original sources

PubMed2006

Two-photon vibrational spectroscopy for biosciences based on surface-enhanced hyper-Raman scattering.

Two-photon excitation is gaining rapidly in interest and significance in spectroscopy and microscopy. Here we introduce a new approach that suggests versatile optical labels suitable for both one- and two-photon excitation and also two-photon-excited ultrasensitive, nondestructive chemical probing. The underlying spectroscopic effect is the incoherent inelastic scattering of two photons on the vibrational quantum states called hyper-Raman scattering (HRS). The rather weak effect can be strengthened greatly if HRS takes place in the local optical fields of gold and silver nanostructures. This so-called surface-enhanced HRS (SEHRS) is the two-photon analogue to surface-enhanced Raman scattering (SERS). SEHRS provides structurally sensitive vibrational information complementary to those obtained by SERS. SEHRS combines the advantages of two-photon spectroscopy with the structural information of vibrational spectroscopy and the high-sensitivity and nanometer-scale local confinement of plasmonics-based spectroscopy. We infer effective two-photon cross-sections for SEHRS on the order of 10(-46) to 10(-45) cm4 x s, similar to or higher than the best "action" cross-sections (product of the two-photon absorption cross-section and fluorescence quantum yield) for two-photon fluorescence, and we demonstrate HRS on biological structures such as single cells after incubation with gold nanoparticles.

Animals↗

PubMed2006

FTIR-microspectroscopy of prion-infected nervous tissue.

The family of transmissible spongiform encephalopathies (TSE), also termed prion diseases, is a group of fatal, neurodegenerative diseases characterized by the accumulation of a misfolded protein, the disease-associated prion protein PrPSc. This glycoprotein differs in secondary structure from its normal, cellular isoform PrPC, which is physiologically expressed mostly by neurons. Scrapie is a prion disease first described in the 18th century in sheep and goats, and has been established as a model in rodents to study the pathogenesis and pathology of prion diseases. Assuming a multitude of molecular parameters change in the tissue in the course of the disease, FTIR microspectroscopy has been proposed as a valuable new method to study and identify prion-affected tissues due to its ability to detect a variety of changes in molecular structure and composition simultaneously. This paper reviews and discusses results from previous FTIR microspectroscopic studies on nervous tissue of scrapie-infected hamsters in the context of histological and molecular alterations known from conventional pathogenesis studies. In particular, data from studies reporting on disease-specific changes of protein structure characteristics, and also results of a recent study on hamster dorsal root ganglia (DRG) are discussed. These data include an illustration on how the application of a brilliant IR synchrotron light source enables the in situ investigation of localized changes in protein structure and composition in nervous cells or tissue due to PrPSc deposition, and a demonstration on how the IR spectral information can be correlated with results of complementary studies using immunohistochemistry and x-ray fluorescence techniques. Using IR microspectroscopy, some neurons exhibited a high accumulation of disease-associated prion protein evidenced by an increased amount of beta-sheet at narrow regions in or around the infected nervous cells. However, not all neurons from terminally diseased hamsters showed PrPSc deposition. Generally, the average spectral differences between all control and diseased DRG spectra are small but consistent as demonstrated by independent experiments. Along with studies on the purified misfolded prion protein, these data suggest that synchrotron FTIR microspectroscopy is capable of detecting the misfolded prion protein in situ without the necessity of immunostaining or purification procedures.

Animals↗

PubMed2006

Surface-enhanced Raman optical activity on adenine in silver colloidal solution.

We report the collection of Raman optical activity (ROA) spectra of adenine in silver colloidal solution, that is, surface-enhanced Raman optical activity (SEROA) using considerably shorter data acquisition times, reduced excitation power, and lower concentration, as compared to classical ROA measurements on molecules of biological interest so far reported in the literature. These improvements in experimental parameters for ROA measurements can be explained by enhanced Raman signals in the local optical fields of the silver nanoparticles and by at least 1 order of magnitude higher values for circular intensity differences (CIDs), as compared to classical ROA that has been suggested before and theoretically discussed in terms of large field gradients near a metal surface. The measured ROA effect for adenine can be understood in terms of adsorption-induced chirality in the prochiral molecules on the silver nanoparticles. Surface-enhanced Raman optical activity offers potential capabilities for sensitive, rapid, stereochemical characterization of basic building blocks of biopolymers, such as amino acids and nucleosides, as well as biologically active molecules, in particular, also for probing organization and self-assembling of such molecules on metal surfaces.

Adenine↗

PubMed2006

Surface-enhanced Raman scattering in local optical fields of silver and gold nanoaggregates-from single-molecule Raman spectroscopy to ultrasensitive probing in live cells.

This Account discusses surface-enhanced Raman scattering at extremely high enhancement levels that can occur for molecules attached to silver and gold nanoclusters. Strongly enhanced and highly confined local optical fields enable surface-enhanced Stokes and anti-Stokes Raman spectroscopy of single molecules even under nonresonant excitation conditions as well as extremely large effective cross sections in two-photon excited Raman spectroscopy. The ability for very sensitive and spatially confined molecular structural probing makes gold and silver nanoclusters very promising tools for studies of small structures in biological materials, such as cellular compartments.

Cells↗

PubMed2006

In vivo molecular probing of cellular compartments with gold nanoparticles and nanoaggregates.

Surface-enhanced Raman (SERS) signatures were measured from single living cells at different times after the uptake of gold nanoparticles. The spectra are indicative of chemical changes in the environment of the nanostructures over time. The increase of the SERS signal strength and parallel TEM studies indicate the formation of nanoaggregates providing optimum SERS enhancement for ultrasensitive probing inside the endosomal compartment. The results have implications for medical and biotechnology applications of SERS nanosensors in cells.

Animals↗

PubMed2005

Dynamics of allostery in hemoglobin: roles of the penultimate tyrosine H bonds.

The tyrosine residues adjacent to the C termini of the hemoglobin (Hb) subunits, alphaY140 and betaY145, are expected to play important structural roles, because the C termini are the loci of T-state quaternary salt-bridges, and because the tyrosine side-chains bridge the H and F helices via H bonds to the alphaV93 and betaV98 carbonyl groups. These roles have been investigated via measurements of oxygen binding, (1)H NMR spectra, resonance Raman (RR) spectra, and time-resolved resonance Raman (TR(3)) spectra on site mutants in which the Hcdots, three dots, centeredF H bonds are eliminated by replacing the tyrosine residues with phenylalanine. The TR(3) spectra confirm the hypothesis, based on TR(3) studies of wild-type Hb, that the Hcdots, three dots, centeredF H bonds break and then re-form during the sub-microsecond phase of the R-T quaternary transition. The TR(3) spectra support the inference from other mutational studies that the alphabeta dimers act as single dynamic units in this early phase, motions of the E and F helices being coupled tightly across the dimer interface. Formation of T quaternary contacts occurs at about the same rate in the mutants as in HbA. However, these contacts are weakened substantially by the Y/F substitutions. Equilibrium perturbations are apparent also, especially for the alpha-subunits, in which relaxation of the Fe-His bond, strengthening of the Acdots, three dots, centeredE interhelical H bond, and weakening of the "switch" quaternary contact in deoxyHb are all apparent. Structural effects are less marked for the beta-chain Y/F replacement, but the Bohr effect is reduced by 25%, indicating that the salt-bridge and H bond interactions of the adjacent C terminus are loosened. The alpha-chain replacement reduces the Bohr effect much more, consistent with the global perturbations detected by the structure probes.

Allosteric Regulation↗

PubMed2005

Optical probes for biological applications based on surface-enhanced Raman scattering from indocyanine green on gold nanoparticles.

We report surface-enhanced Raman scattering (SERS) studies on indocyanine green (ICG) on colloidal silver and gold and demonstrate a novel optical probe for applications in living cells. In addition to its own detection by the characteristic ICG SERS signatures, the ICG gold nanoprobe delivers spatially localized chemical information from its biological environment by employing SERS in the local optical fields of the gold nanoparticles. The probe offers the potential to increase the spectral specificity and selectivity of current chemical characterization approaches of living cells and biomaterials based on vibrational information.

Animals↗

PubMed2003

In situ identification of protein structural changes in prion-infected tissue.

Transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative disorders characterized by the conversion of the normal prion protein (PrP(C)) into aggregates of its pathological conformer (PrP(Sc)). The mechanism behind this structural conversion is unclear. We report the identification of disease-related protein structural differences directly within the tissue environment. Utilizing a synchrotron infrared (IR) light source, IR images of protein structure were obtained at a subcellular resolution, revealing regions of decreased alpha-helical content and elevated beta-sheet structure in and around infected neurons in the 263 K scrapie hamster model. PrP(Sc) immunostaining of the same tissue demonstrated that the elevated beta-sheet regions correspond to regions where the misfolded structure of PrP(Sc) is located. No evidence of these structural changes was observed in normal neurons.

Animals↗

PubMed2002

Molecular changes of preclinical scrapie can be detected by infrared spectroscopy.

Infrared (IR) microspectroscopy was used to detect disease-associated molecular changes spatially resolved in cryosections of scrapie-infected tissue of the CNS. The results show that IR spectra can be used for the discrimination between normal and 263K scrapie-infected hamster nervous tissue not only in the terminal stage of the disease but also in early clinical and even in the preclinical stage at 90 d after oral infection. The nuclei of the cranial nerves located in the medulla oblongata were especially well suited for an early detection of the diseased state by IR microspectroscopy. The most prominent molecular changes indicated by the IR spectra were located between 1300 and 1000 cm(-1), a region that contains contributions primarily from carbohydrates and the phosphate backbones of nucleic acids but also from membrane constituents.

Administration, Oral↗