Quantum Interference in the Vibrational Relaxation of the O-H Stretch Overtone of Liquid H2O

Extraction of DNA from trace forensic samples with a modified lysis buffer and chitosan coated magnetic beads

The trace amounts of human tissue cells or body fluids left at the crime scene are often mixed with inhibitors such as rust, pigments, and humic acid. The extraction of the DNA from the trace cells is crucial for the investigation of cases. Usually, specially designed magnetic nanoparticles were chosen by the case investigators to enrich and elute DNA, which was then used for polymerase chain reaction (PCR) and short tandem repeat (STR) analysis. The traditional approach often had the following problems, such as low DNA enrichment efficiency, possible DNA breakage, and complex operations. Here, the 1%(w/v) of chitosan (75% deacetylation degree) was used to modify the 50 nm magnetic nanoparticles to gain the Chitosan@Beads, which theoretically carried positively charged in the pH = 5 of lysis buffer so as to adsorb negatively charged DNA through electrostatic interactions. The XPS and FT-IR results demonstrated that chitosan was successfully attached to the surface of magnetic nanoparticles. A set of simulated samples, containing 20 mg/μL of humic acid, pigments, iron ions (Fe2+, Fe3+), and the coexistence of the above three substances, were prepared to simulate the case scene. Human bronchial epithelial cells were mixed with the 200 μL of the above simulated samples for DNA extraction. 400 μL of lysis buffer, 20 μL of proteinase K (10 mg/mL) and 20 μL of Chitosan@Beads solution (20 mg/mL) was used for cell disruption and DNA enrichment. The extraction sensitivity of Chitosan@Beads was confirmed to be 10 cells, superior to commercial reagent kits. The Chitosan@Beads@DNA can directly use for "In-situ PCR" with elution-free operations. The STR loci rate of DNA extracted by Chitosan@Beads was around 97.9%, higher than the commercial kit (66.7%). In short, we foresee here developed novel Chitosan@Beads and modified lysis buffer could provide a new model for the DNA extraction of forensic trace evidence.

Ultra-high resolution near-infrared spectrum by wavelet packet transform revealing the hydrogen bond interactions

Resolution is always an obstacle to analyzing the fine structure of a spectrum. The problem is particularly serious in the analysis of the near-infrared (NIR) spectra of aqueous solutions, because the spectrum is generally composed of overlapping broad peaks making the understanding of the structures and the interactions notoriously difficult. In this work, wavelet packet transform (WPT) was adopted to enhance the resolution of the NIR spectra of aqueous mixtures. Due to the microscopic ability of WPT in both position and frequency, the fine details of a spectrum can be observed in the spectral components of different frequencies obtained by WPT decomposition. Ultra-high resolution spectrum can be obtained from the high-frequency component representing the spectral features. Spectral features of different hydrogen-bonded OH, as well as the OH in HOH and HOD, were identified from the high-resolution NIR spectra of water and heavy water mixtures and validated by the variation of the spectral intensity with the mole ratio of H₂O and D₂O. The high-resolution spectrum was further applied in analyzing the interaction of amine and water. The spectral features of the hydrogen bonding between CH/NH in tert-butylamine (TBA) and OH in water were observed. The structures of CH bonded to one water molecule, and the structures of NH connecting with one and two water molecules were identified.

Surface amplification of tetraphenylporphyrin overtone and combination Raman bands in drop coating deposition Raman (DCDR) on electrically conductive surfaces

It is essential to realize a Raman measurement technique without artifact or fluorescence signals for high-quality and reliable data in a valid molecular-level analysis and interpretation. This requirement applies especially to a molecule with strong fluorescence like porphyrin. Here, the surface of a gold substrate performs better as a DCDR substrate for tetraphenylporphyrin than other surfaces, such as tantalum, indium tin oxide glass, or aluminium. Polarized Raman spectra of tetraphenylporphyrin demonstrated the oriented deposition of porphyrin crystallites on the Au substrate using the drop coating technique. The emission anisotropy suggests that the deposited crystallites are arranged outward radially with the porphyrin ring orientation. The orientation is signed by the NHHN axis that is parallel to the radial vector along the X-axis. Moreover, it also demonstrates high chemical stability after preservation and repeated measurements. The Raman signal on a gold substrate is enhanced more than on other substrates beyond mere preconcentration of analytes or the coffee-ring effect only, which might be due to the contribution of the SERRS effect. This effect will be discussed based on the interactions among localized surface plasmons, vibronic transitions, and Raman active vibrational modes.

Controlled modification of biomolecules by ultrashort laser pulses in polar liquids

Targeted chemical modification of peptides and proteins by laser pulses in a biologically relevant environment, i.e. aqueous solvent at room temperature, allows for accurate control of biological processes. However, the traditional laser methods of control of chemical reactions are applicable only to a small class of photosensitive biomolecules because of strong and ultrafast perturbations from biomolecule-solvent interactions. Here, we report excitation of harmonics of vibration modes of solvent molecules by femtosecond laser pulses to produce controlled chemical modifications of non-photosensitive peptides and proteins in polar liquids under room conditions. The principal modifications included lysine formylation and methionine sulfoxidation both of which occur with nearly 100% yield under atmospheric conditions. That modification occurred only if the laser irradiance exceeded certain threshold level. The threshold, type, and extent of the modifications were completely controlled by solvent composition, laser wavelength, and peak irradiance of ultrashort laser pulses. This approach is expected to assist in establishing rigorous control over a broad class of biological processes in cells and tissues at the molecular level.

Electrical anharmonicity in hydrogen bonded systems: complete interpretation of the IR spectra of the Cl-H[combining right harpoon above] stretching band in the gaseous (CH3)2OHCl complex

Following the previous developments to simulate the fully infrared spectra of weak hydrogen bond systems within the linear response theory, an extension of the adiabatic model is presented here. A general formulation including the electrical anharmonicities in the calculation of the damped autocorrelation function of weak H-bonds is adopted to facilitate the support of the additional properties, and thus the IR spectra of the Cl-H[combining right harpoon above] stretching band in the gaseous (CH₃)₂OHCl complex. We have explored the origins of the broadening of the Cl-H[combining right harpoon above] stretching band. We found that the main features of the lineshape are attributed to electrical anharmonicity as a consequence of the large mixed second derivatives of the dipole moment with respect to the Cl-H[combining right harpoon above] bond and of the intermonomer elongations . In addition to providing more accurate theoretical band shapes, inclusion of the electrical anharmonicity in the present model paves the way for a more complete interpretation by generating three new Franck-Condon superposed distributions.