Raman spectroscopy

Raman spectroscopy based activities were developed and implemented into the first year
chemistry undergraduate curriculum. The implementation of these experiences and
experiments and the utility of Raman spectroscopy as a teaching tool to convey anchoring
chemistry concepts using a hands-on Raman spectroscopy based approach are discussed.
Fundamental principles of chemistry, such as the interaction of light with matter, molecular
bonding, equilibrium, and acid base reactions are facilitated through use of these Raman
spectroscopy based experiments and experiences. An assessment of student learning gains
as a result of participation in a Raman spectroscopy experience was also conducted and is
discussed.

Cell penetrating peptides (CPPs) are short sequences of amino acids that excel in
crossing the cellular membrane without inducing cytotoxicity Interest in these peptides
stem from their ability to be attached, and grant their penetrating properties to, a variety
of cargo In this work we have combined the application of Confocal Raman Microscopy
(CRM) and Atomic Force Microscopy for the first time to examine the interactions of
unlabeled Transportan (TP), one of the most well studied CPPs, with mammalian cells
CRM’s capability to discriminate control and treated cell groups was verified by principal
component analysis (PCA) and linear discriminant analysis (LDA) and was 93-100%
accurate We’ve determined that at a concentration of 20 μM TP enters cells through a
non-endocytotic mechanism, has a high affinity for the cytoplasm and membranes, and
results in a significant increase in cellular stiffness Our work provides the first direct
evidence of this cell-stiffening phenomenon SFTI-1, the smallest member of a bicyclic, cysteine rich class of CPPs, was
examined by CRM to determine the potential role of cyclic structure on cellular uptake
The peptide, along with monocyclic and linear analogs was heavy isotope labeled and
incubated with mammalian cells at numerous concentrations and timespans Our work is
the first SFTI-1 uptake study forgoing the use of fluorophore conjugates, which have
been linked to artificial cellular uptake We demonstrate herein the absence of any CRM
detectable uptake, providing the first evidence that SFTI-1 may not be a CPP
Finally, CRM was applied to the discrimination of normal and basal cell
carcinoma cells obtained from the same donor The use of patient matched cells avoids
the normal biochemical variations that exist among individuals, ensuring that
discrimination is based solely on the cell’s diseased state CRM spectra, analyzed by
PCA and LDA, were capable of spectral discrimination with 100% accuracy Major
differences in the cancerous cells were an increase in lipids and nucleic acids, and an
overall decrease in protein We also demonstrate an enhancement in Raman signal
through the use of an aluminum foil substrate, providing a practical approach for
measuring cells with thin morphologies

G-quadruplexes (G4s) are nucleic acid structures formed from π-stacked planar sets of four Hoogsteen hydrogen bonded guanine bases. G4s emerged as potential therapeutic targets based on their ability to modulate gene expression and inhibit the ability of telomerase to elongate chromosomal telomeres. Raman spectroscopy, polarized Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), and other optical spectroscopic techniques were used to characterize the G4s formed by four different DNA sequences: human telomeric (HT), thrombin-binding aptamer (TBA), nuclease hypersensitive element III1 region of the c- Myc gene promoter (Myc), and a single loop-isomer of Myc (MycL1).

Polycrystalline bulk samples with the chemical formula YBa2(Cu1-xFex)3O7+delta were fabricated by the standard solid-state reaction method, and studied through magnetic susceptibility and Raman scattering experiments. In the Raman experiments, the Cu(1)-O(1) c-axial Ag stretching mode at ~502cm^-1 was investigated extensively at temperatures ranging from 23K to 773K. The room-temperature Raman spectra indicated a trend for saturation in frequency shift (as a function of iron concentration). This was interpreted as evidence supporting the occurrence of a type of iron clustering in the (001) basal plane. Effects of such a cluster formation upon the mechanism of superconductivity were considered. The low temperature Raman spectra show that the 502cm^-1 mode frequency increased slightly with decreasing temperature for all of the studied values of iron concentration without exhibiting any anomalous behavior. In the high temperature Raman spectra, a significant softening of the 502cm^-1 mode, indicative of a phase transition onset, was observed.

Raman spectroscopy was used to determine the phase structure and phase stability of zirconia mixtures for various elevated temperatures, type and concentration of oxides added to zirconia, and fabrication process. All 8 wt.% yttria samples showed mostly the tetragonal structure at room temperature. Three of the four 8 wt.% yttria samples exhibited the tetragonal structure at elevated temperatures, while no conclusion was inferred for the powdered sample. As compared with yttria, ceria is a less effective stabilizer with respect to the zirconia tetragonal structure. A monoclinic transformation between 400 K and 800 K was observed in the 4 wt.% yttria sample which had been processed by rapid quenching. Adding alumina to 4 wt.% yttria did not completely stabilize the tetragonal structure at or above room temperature, making it a less effective stabilizer than yttria or ceria. The phase transformation was responsible for the unusual values in the Gr uneisen parameters obtained for the 4 wt.% yttria sample.

The Raman spectra of ammonia solid I and II were studied
in the lattice and intramolecular region. The study of the internal modes of phase I suggests the presence of
disorder in the ordered phase. The lattice modes of
phase II are, for the first time, carefully reported as
two very broad lines superimposed on an overdamped
feature. The results confirm the structure previously
determined by neutron scattering and NMR that phase II is
a typical disordered phase with space group P6,3/mmc. A
mode assignment was tentatively made and Gruneisen
parameters of the two assumed translational modes
calculated. In terms of the Michel-Naudts theory of
rotational-translational interactions, phase II is in the
slow relaxation regime. A four-band model was used for
the intramolecular stretching region.

The frequencies of three lattice vibrational nodes of solid
ammonia I were measured as functions of temperature and molar
volume, via Raman spectroscopy. Calculated Gruneisen parameters
of 2.6, 2.4, and 0.8, for modes with frequencies near
108 cm^-1 , 140 cm^-1 and 306 cm^-1 , respectively, identify the
first two modes to be translational and the third librational
in accordance with previous assignments. The Gruneisen parameter
of the libration is lower than expected for purely octopolar
electrostatic interactions between molecules. The
change in frequency with temperature of all three modes is
due to their interaction with the mode near 108 cm^-1. The lifetimes
of both translations are determined by their rate of
combination with librations near 306 cm^-1
and 313 cm^-1. The lifetime of the libration near 306 cm^-1 depends on its rate of
combination with the two translations (108 cm^-1 and 140 cm^-1) and a libration near 440 cm^-1.

Cell penetrating peptides (CPPs) have drawn the attention of researchers due to their ability to internalize large cargos into cells including cancer cells. The mechanism(s) with which the peptides enter the cell, however, is/are not clear and full of controversy. The peptide conformations and their microenvironment in live cells had been unknown until the development of a technique developed in our lab. As a first demonstration of principle, penetratin, a 16-residue CPP derived from the Antennapedia homeodomain protein of Drosophila, was measured in single, living melanoma cells. Carbon-13 labeling of the Phe residue of penetratin was used to shift the intense aromatic ring-breathing vibrational mode from 1003 to 967 cm-1, thereby enabling the peptide to be traced in cells. Difference spectroscopy and principal components analysis (PCA) were used independently to resolve the Raman spectrum of the peptide from the background cellular Raman signals.