An infrared spectroscopic study of C7 intramolecular hydrogen bonds in peptides

The ir-spectra in the N-H stretching region of Piv-Pro-NHMe and Boc-Pro-NHMe have been studied in carbon tetrachloride and chloroform solutions over a wide range of concentrations. Based on the concentration dependence of the N-H stretching bands, it has been shown that the characteristic N-H stretching band due to the C7 intramolecular hydrogen bond is around 3335 cm-'. Intermolecular hydrogen bonding also occurs to a small extent in these peptides, giving rise to a slight concentration dependence of the N-H stretching bands. The band around 3335 cm-* need not necessarily be due to C7 hydrogen bonds alone as proposed by Tsuboi et al. or to intermolecular hydrogen bonding alone as proposed by Maxfield et al.; this conclusion is supported by studies on Boc-Leu-NHMe, which undergoes only intermolecular hydrogen bonding We have shown that 2-Aib-Aib-OMe and Z-Aib- Ala-OMe form C7 intramolecular hydrogen bonds in addition to C5 intramolecular hydrogen bonds. The present studies also show that all the peptides studied exist in more than one conformation in solution.

Infrared spectroscopic study of the phase transitions in CsNO3, RbNO3 and NH4NO3

Phase transitions of CsNO3 (II-I), RbNO3 (IV-III-II) and NH4NO3 (V-IV-III-II-I) have been studied by i.r. spectroscopy. The study has provided useful information on the changes in the dispositions of the ions during the phase transitions.

Infrared and Nuclear Quadrupole Resonance Studies of the Phase Transitions of Para-dichlorobenzene

The α→γ→α→β transitions of para-dichlorobenzene have been studied by employing infrared and n.q.r. spectroscopy as well as differential scanning calorimetry. The γ phase is associated with considerably higher values of some of the intramolecular vibration frequencies. The α→γ transition shows athermal nucleation behaviour as in martensitic transitions. Intermolecular vibration bands around 46 and 85 cm–1 present in γ and α phases disappear in the β phase. The α→β transition seems to be associated with some orientational disorder.

Frequency-comb-referenced molecular spectroscopy in the mid-infrared region

A simple method for absolute frequency measurements of molecular transitions in the mid-infrared region is reported. The method is based on a cw singly-resonant optical parametric oscillator (SRO), which is tunable from 3.2 to 3.45 µm. The mid- infrared frequency of the SRO is referenced to an optical frequency comb through its pump and signal beams. Sub-Doppler spectroscopy and absolute frequency measurement of the P(7) transition of the ν3 band of CH4 are demonstrated.

An infrared spectroscopic study of the low-spin-high-spin transition in FexMn1-x(Phen)2(NCS)2: A composition-induced change in the order of the spin-state transition

Infrared spectroscopy provides a valuable tool to investigate the spin-state transition in Fe(II) complexes of the type Fe(Phen)2(NCS)2. With progressive substitution of Fe by Mn, the first-order transition changes over to a second-order transition, with a high residual population of the high-spin state even at very low temperatures

Synthesis, infrared spectra and thermoanalytical properties of transition metal sulfite hydrazine hydrates

Transition metal sulfite hydrazine hydrates, MSO3·xN2H4·yH2O whereM=Mn, Fe, Co, Ni and Zn have been prepared and characterized by chemical analysis, infrared spectra, thermoanalytical and combustion studies. The colours,x andy parameters of the complexes varied depending upon the preparation conditions. Thermal decomposition characteristics differ from metal to metal yielding metal oxides at relatively low temperatures.Mittels chemischer Analyse, IR-Spektren, thermoanalytischen und Verbrennungsstudien wurden die Hydrazinhydrate der hergestellten Übergangsmetallsulfite MSO3·xN2H4·yH2O mitM=Mn, Fe, Co, Ni und Zn beschrieben. Farbe sowie die Parameterx undy der Komplexe hängen von den Herstellungsbedingungen ab. Die thermische Zersetzung, bei der bei relativ niedrigen Temperaturen Metalloxide entstehen, ist von Metall zu Metall verschieden.

Infrared divergences and confinement in massive (2+1)-dimensional QED

In (2+1)-dimensional quantum electrodynamics with massless photons and massive matter fields, it is shown that the mass renormalization of the latter is infrared divergent at one loop. This result remains unchanged at two loops. A simple argument based on a similar divergence of the Coulomb potential leads us to conjecture that charged states are not observable in this model. This argument holds in 1+1 dimensions also.

An infrared spectroscopic study of the orientational phase transitions of C70

Infrared spectroscopic studies of C70 films show variation in absorbance and linewidth of the bands across the orientational phase transitions around 280 and 340 K. There is some evidence for the coexistence of phases in the 210–270 K region and for the occurrence of another transition below 200 K.

Model Based Target Tracking in a Wireless Network of Passive Infrared Sensor Nodes

We consider the problem of tracking an intruder in a plane region by using a wireless sensor network comprising motes equipped with passive infrared (PIR) sensors deployed over the region. An input-output model for the PIR sensor and a method to estimate the angular speed of the target from the sensor output are proposed. With the measurement model so obtained, we study the centralized and decentralized tracking performance using the extended Kalman filter.

Dynamic structure of charge carrier in polyaniline by near-infrared excited resonance Raman spectroscopy

New vibrational Raman features characteristic to the conductive form of polyaniline have been observed with the near-infrared excitation at 1047 nm. Based on an analogy with the resonance Raman spectrum of Michler's ketone in the lowest excited triplet (T-1) state, we consider these features as due to a dynamic structure of a diimino-1,4-phenylene unit in the polyaniline chain exchanging a positive charge very rapidly. This consideration directly leads to a conducting mechanism in which a positive charge migrates from one nitrogen to the other through the conjugated chain of polyaniline.

An investigation of the first-order spin-state transition in Fe(Phen)(2)(NCS)(2) EXAFS and infrared spectroscopy

The structure of Fe(Phen)(2)(NCS)(2) has been examined across the first-order spin-state transition by EXAFS with full multiple scattering analysis. The EXAFS data at 298 K can be satisfactorily assigned to the high-spin state, but the analysis of the low-temperature data at 90 K is not entirely unequivocal, although consistent with the predominant presence of the low-spin state. That some proportion of the high-spin state remains at low temperatures, well below the first-order transition, is clearly evidenced in the infrared spectra, suggesting possible sublattice ordering.