Strong and weak effects caused by non covalent interactions between chloroform and selected electron donor molecules.

The FTIR spectra of chloroform (Cl(3)CH) in mixtures with various electron donors (B = CH(3)CCH, HCCH, NCCD(3), ClCD(3) and CO) have been studied in liquefied Kr. Spectroscopic evidence of weak H-bond formation has been found. The relative stability of some complexes has been evaluated from temperature studies of integrated intensities of vibrational bands attributed to monomer and complex species. A weak red shift of the stretching vibration of chloroform involved in H-bonding with CH(3)CCH and HCCH having π-electron area was observed. However, in the case of interactions with NCCD(3) and CO, a weak blue shift was detected. In most of the cases, a noticeable increase in the integrated intensity of the CH stretching band was found. Ab initio MP2/6-311++G(2d,2p) a priori counterpoise corrected calculations have been performed for a series of Cl(3)CH and B. Stationary points at the potential energy surface were examined and the structures related to the real minima have been found. The calculations reproduce the majority of experimental results. It has been found that the commonly used correlation between the frequency shift of the CH stretching vibration of the proton donor subunit and the change in CH bond length can fail in the case of the complexes characterized by a weak frequency shift effect.

Proton transfer reaction of a new orthohydroxy Schiff base in some protic and aprotic solvents at room temperature and 77 K.

The ground and excited state proton transfer reactions of a new orthohydroxy Schiff base, salicylidine-3,4,7-methyl amine (SMA) has been studied by means of absorption, emission and time resolved fluorescence spectroscopy in some polar protic and aprotic solvents at room temperature and 77K. The spectral behavior of SMA has been investigated both in neutral and basic conditions. The intramolecularly hydrogen bonded enol and zwitterion have been detected in pure methanol and ethanol, the anion is detected in basic condition. At 77K, SMA shows phosphorescence in pure methanol and ethanol. From nanosecond measurements and quantum yields of fluorescence, we have estimated the decay rates of proton transfer reaction in methanol and ethanol.

Synthesis, analgesic activity and computational study of new isothiazolopyridines of Mannich base type.

A series of new 4-arylpiperazine derivatives of isothiazolopyridine of Mannich base type and their non-4-arylpiperazine analogues (3 and 4) were synthesized and assayed as potential analgesic agents. Pharmacological assay demonstrated that all the compounds prepared, without exception, displayed significant activity in the mouse writhing assay. The analgesic action, expressed as ED50, was found to be 2-10 times more potent than that of acetylsalicylic acid and 1.5-10 times weaker than that of morphine, these being used as standards. The toxicities (LD50) of the investigated derivatives varied and ranged from 250 to 2000 mg/kg. Additionally, the computational investigations were performed in order to find correlation between molecular structure and biological effects (toxicity, analgesic action) of discussed compounds. Useful model was found for toxicity assessment.

Infrared spectra and relative stability of the F3CH/NH3 H-bonded complex in liquefied Xe.

FTIR spectra of mixtures of fluoroform (F3CH) and ammonia (NH3), have been studied in liquid xenon between 5400 and 500 cm-1. Spectroscopic evidence for the formation of a hydrogen bonded complex has been found and the complexation enthalpy Delta(LXe)H degrees in the temperature interval between 173 and 215 K, was determined to be 14.4 (7) kJ mol-1. The parallel fundamentals nu1 and nu2 of ammonia reveal a strong narrowing effect upon complex formation, whereas the perpendicular fundamentals nu3 and nu4 show a modest decrease of their width. CP corrected ab initio calculations at the MP2(FULL)/6-311++G(3df,2pd) level predict a linear geometry for the complex, characterized by a small red shift of the CH stretch frequency of fluoroform. The ab initio interaction energy was found to be compatible with the isolated molecule complexation energy extrapolated from the experimental Delta(LXe)H degrees .

Tautomerism of sterically hindered schiff bases. Deuterium isotope effects on 13C chemical shifts.

A series of sterically hindered o-hydroxy Schiff bases derived from o-hydroxyaceto- and benzophenones with very short intramolecular hydrogen bonds were described qualitative and quantitatively by deuterium isotope effects on (13)C chemical shift, (n)DeltaC(XD), (n)DeltaF(XD), (1)J(N,H) coupling constants, deltaNCH(3) chemical shifts and UV spectra. All the investigated compounds are found to be tautomeric. The tautomeric character is described by the signs of the deuterium isotope effects on the (13)C chemical shifts. For the 3-nitro-5-chloro derivatives at low temperature, the equilibrium is shifted almost fully toward the proton transferred form in CD(2)Cl(2). Intrinsic deuterium isotope effects on chemical shifts of these compounds as well as (1)J(N,H) coupling constants suggest that a zwitterionic resonance form is dominant for the proton transferred form. Structures, (1)H, (19)F, and (13)C chemical shifts, and deuterium isotope effects on (13)C chemical shifts are calculated by ab initio methods. The potential energy functions and the total deuterium isotope effects are calculated, and they are shown to correspond well with the experimental findings.

Structural manifestations of proton transfer in complexes of 2,6-dichlorophenols with pyridines.

DFT B3LYP/6-31G(d,p) calculations were performed to describe the proton transfer reaction pathway in the 2,6-dichlorophenolate of pyridine. The aim of these calculations was to establish the character of the dependence of the structure parameters on the proton transfer and comparing the results with known structures, e.g. the 2,6-dichloro-4-nitro- and pentachlorophenolates of pyridines. To make this comparison more reliable, the calculations were repeated with the use of a reaction-field correction with the Onsager radius and electric permittivity taken from the solid-state measurements. The calculations show that the second approach gives a better description of the structural modifications during the proton transfer.

Interaction between methyl glyoxal and ascorbic acid: experimental and theoretical aspects.

The absorption spectral change of methyl glyoxal (MG) due to the interaction with ascorbic acid (AA or Vitamin C) has been investigated using steady-state spectroscopic technique. A plausible explanation for the spectral change has been discussed on the basis of hydrogen bonding interaction between the two interacting species. The equilibrium constant for the complex formation due to hydrogen bonding interaction between MG and AA has been obtained from absorption spectral changes. Ab inito calculations with DFT B3LYP/6/31G (d,p) basis sets have been used to find out the molecular structure of the hydrogen bonded complex. The O...H distance found in the O-H...O hydrogen bond turns out to be quite short (1.974 A) which is in conformity with the large value of the equilibrium constant determined experimentally.

Proton transfer reaction of a new orthohydroxy Schiff base at room temperature and 77 K.

One new orthohydroxy Schiff base, 2-(N-benzyl-alpha-iminoethyl)naphthol (BEIN) has been synthesized. The proton transfer reaction of BEIN has been investigated by means of absorption, steady state and time resolved fluorescence spectroscopy in different solvents at room temperature and 77K. The behavior of BEIN in ethanol and water, has been studied in neutral, acidic and basic conditions. Excited state intramolecular proton transfer (ESIPT) is evidenced by a large Stokes shifted ( approximately 11,000 cm-1) fluorescence in solid crystalline media at room temperature. We present the observation of phosphorescence both in non-polar and protic solvents at 77K. The observed decay dynamics of the phosphorescence and delayed fluorescence indicates that the triplet state can be attributed to the cis-keto form. The molecular structures are determined by B3LYP/6-31G** calculation. From theoretical study it is suggested that the strengthening of hydrogen bond result from the steric repulsion of the phenyl ring. The presence of benzene ring increases the proton transfer barrier in case of BEIN compared to previously studied 7-ethylsalicylidenebenzylamine (ESBA).

Excited state proton transfer reaction of two new intramolecularly hydrogen bonded Schiff bases at room temperature and 77K.

Two new orthohydroxy Schiff bases, 7-phenylsalicylidene benzylamine (PSBA) and 7-ethylsalicylideneaniline (ESA) have been synthesized. The excited state intramolecular proton transfer (ESIPT) and the structure of PSBA and ESA in its crystalline form and in the solvents n-hexane, n-heptane and 1,4-dioxane have been investigated by means of absorption, emission and nanosecond spectroscopy at room temperature and 77K. One ground state species has been detected both in neutral and basic solutions of both PSBA and ESA: the cis-enol form with an intramolecular hydrogen bond. The ESIPT and formation of keto tautomer are evidenced by a large Stokes shifted emission (approximately 12000 cm(-1)) at room temperature only in the case of ESA. On the other hand the keto tautomer is the predominant species at 77K in a solid matrix and as a solid sample at room temperature both in the case of ESA and PSBA. In the case of both ESA and PSBA the more intense, higher energy emission is due to the species which has not undergone ESIPT and attributed mainly due to cis-enol form. The trans-enol form is also observed by changing the excitation wavelength. Both the compounds are found to undergo a structural change to a zwitterionic and intermolecular hydrogen bonded form in the presence of a strong base like triethylamine. From the nanosecond measurements and quantum yield of fluorescence we have estimated the decay rates of proton transfer reaction in the case of PSBA. Our theoretical calculation at the AM1 level of approximation shows that the ground singlet state has a rather large activation barrier both in the case of PSBA and ESA. The barrier height is much lower on the corresponding excited singlet surface only in the case of ESA. The process is predicted to be endothermic in the ground state and exotherrmic in the excited singlet state.

Proton transfer reaction of a new orthohydroxy Schiff base in protic solvents at room temperature.

Ground and excited state inter- and intramolecular proton transfer reactions of a new o-hydroxy Schiff base, 7-ethylsalicylidenebenzylamine (ESBA) have been investigated by means of absorption, emission and nanosecond spectroscopy in different protic solvents at room temperature and 77 K. The excited state intramolecular proton transfer (ESIPT) is evidenced by a large Stokes shifted emission (approximately 11000 cm(-1)) at a selected excited energy in alcoholic solvents. Spectral characteristics obtained reveal that ESBA exists in more than one structural form in most of the protic solvents, both in the ground and excited states. From the nanosecond measurements and quantum yield of fluorescence we have estimated the decay rate constants, which are mainly represented by nonradiative decay rates. At 77 K the fluorescence spectra are found to be contaminated with phosphorescence spectra in glycerol and ethylene glycol. It is shown that the fluorescence intensity and nature of the species present are dependent upon the excitation energy.

Immunological activity of new heterocyclic amides of 5-amino-3-methylisoxazole-4-carboxylic acid.

In the present study, some new amides of 5-amino-3-methylisoxazole-4-carboxylic acid were obtained. All new structures possessed markedly different groups of electron acceptor character, different spatial structure and they contained nitrogen heteroatom, enabling formation of salts and, at the same time, higher biological availability. They were examined for immunomodulating activity in comparison with cyclosporine A (CsA). We investigated effects of the compounds on the lipopolysaccharide (LPS)-induced production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) by human peripheral blood cells. Some compounds exhibited suppressory action which corresponded with increasing electronoacceptor nature of the amide substituent. Two compounds, characterized by flat aromatic rings, demonstrated quite different properties. Much higher activity was expressed by compounds which contained -NH group, the group which conditioned immunostimulatory activity in other compounds described previously.

Walking through a maze alters the architecture of sleep.

Human and animal studies imply that sleep is a critical period for consolidation of recent memories. Whereas the majority of researchers focussed on the procedural learning, the present human study concerns how storing of spatial information and episodic memory are linked to sleep stages. Two city mazes, a simple and a complex one, were created by means of a computer program. Local aspects of these mazes appeared as street scenes on a TV-screen. Our subjects sat in front of the screen and manoeuvered through the maze by the help of a three-button PC mouse. Thus, each subject took a 'mental walk' through an imaginary city. The task was to find various end-points and to find the way back to the starting point. Subjects of two experimental groups 'walked' through either the simple or complex city maze for eight hours. Afterwards the subjects slept in our laboratory, where their sleep stages could be measured polygraphically. Subjects who had explored the simple maze showed considerable alteration in sleep architecture. They remained significantly longer in sleep Stage 2 than subjects who had explored the complex maze. Moreover, with successful orientation in the simple maze sleep stages occurred aperiodically, whereas walking through the complex maze was associated with sleep stages in accordance with ultradian cycles, as observed in a control group. Compared to subjects of the control group who had experienced neither maze, the subjects of both experimental groups had significantly enhanced EEG sleep spindle activities. Alteration in temporal architecture of sleep and selective prolongation of sleep Stage 2 following spatial orientation point to a functional linkage between cognitive mapping of space and sleep Stage 2 with enhanced EEG spindle activity.

Lateralized ultradian rhythms of the right and left brain: temporal variations of tactile discrimination tested in German subjects.

Endogenous ultradian rhythms with a periodicity of 2-3 hours operate separately in the right and left hemispheres of the human brain and modulate physiological functions, perception and cognition. Since sensory pathways from either hand terminate in the contralateral hemisphere, ultradian rhythms of the right and left brain can be monitored by variations in the tactile discrimination of the left and right hand, respectively. Thirteen right-handed German males were tested every 15 minutes for 8 hours. Time series of the tactile error rate determined for the right and left hands oscillate with significantly different ultradian periodicities. Whereas cycles in tactile discrimination of the right hand (left hemisphere) have a periodicity of about 2 hours, tactile discrimination of the left hand (right hemisphere) is modulated by longer periods of about 3 hours. This is interpreted in terms of the overall functional asymmetry of the human brain. Since the left brain is the specialized locus for verbal processing and the right brain for visual-spatial processing, lateralized ultradian rhythms operating in the hemispheres may provide a distinct frame for long-term timing of neuronal processes underlying semantic and spatial mapping of the environment. This is particularly important for interpreting biosocial behavioural rhythms seen in humans living under natural conditions.

Lateralized ultradian rhythms in time and space: a chronobiological field study in Kenyan Maasai.

Lateralized ultradian rhythms oscillating separately in the right and left hemispheres of the human brain can be monitored by variations in the tactile discrimination of either hand. A previous study in male German subjects has shown that the tactile error rates determined for the right and left hands oscillate with significantly different periodicities. In the present study, a group of Kenyan Maasai shepherds was tested while the subjects were leading herds on daily feeding routes. The Maasai exhibit considerable ultradian rhythms of about 2 hours in tactile error rates of either hand, but in contrast to the German subjects there is no significant difference between the right and left side. While an individual is en route, his hemispheres proceed through alternating states in matching segments of the path. Ultradian rhythms thus 'scan' not only the time of day but also the space, and might provide an intrinsic time-frame for neuronal processes of cognitive mapping.

Lateralized ultradian rhythms: evidence from tactile discrimination of either hand.

Endogenous ultradian rhythms with periods of one or a few hours affect not only on physiological and behavioural functions but also perception and cognition. In particular, lateralized ultradian rhythms which seem to operate separately in the right and left hemispheres of the brain can be monitored by testing the tactile discrimination of the contralateral hand. The present paper is based on two subsequent studies: First, ultradian rhythms in tactile discrimination of either hand were examined in German subjects under laboratory conditions. Considerably different ultradian periods of right and left-handed tactile error rate were found in men but not in women. In a second study, a group of Kenyan Masai shepherds were tested while the subjects were leading herds on daily feeding routes through a savanna habitat. They showed ultradian periods of about 2 hours in tactile discrimination of either hand. Since the right hemisphere is specialized for visuospatial, the left for verbal processing lateralized ultradian rhythms may serve for a long-scale timing of neural processes underlying spatial and semantic mapping of the environment. Sex difference in German subjects and lateral differences found in left-handed (right-hemispheric) ultradian rhythms of German and Masai subjects are discussed from this point of view.

Mental walking through a complex maze influences lateralized ultradian rhythms.

Subjects of two experimental groups, 10 males and 10 females in each group, explored artificial environments represented by compact city mazes. The mazes, a simple and a complex one, were generated by means of a computer program. After turning the program on, a scene with houses, streets, and alleys appeared on a TV screen. The subjects sat in front of the screen and manoeuvered through the simple or the complex maze with the help of a hand-operated device. Correspondingly the street scenes changed in such a way that the subject had the illusion of a normal pace. Each subject explored one maze for eight hours. Every 15 min. an experimenter interrupted the subject's walk and measured tactile discrimination in either hand. Ultradian periodic variations in the tactile error rate of the right and left hands with periods of 2 or 3 hours are found. They are considered manifestations of endogenous rhythms operating separately in the left and right cerebral hemispheres. As demonstrated in a previous paper, lateralized ultradian rhythms in tactile discrimination are different for males and females when tested under quiet laboratory conditions. The present paper shows that the rhythms are specifically influenced in both sexes by the spatial complexity of an artificial environment (maze). These findings are discussed from an evolutionary point of view.

The adaptive significance of social synchronisation of ultradian behaviour cycles: a computer model.

Daily behaviour patterns in a hunter-gatherer community of Colombian Indians show that individual activities are regulated by ultradian behaviour cycles of about 2 hr and that these cycles can be synchronised by social interaction. A computer model was developed which simulated an artificial community and generated dynamic portraits of locomotor activity and social aggregation similar to those of the observed community of Colombian Indians. Social phase-locking of ultradian behaviour cycles occurred, contributing to the safety of group members and their economy of effort in gathering and related activities. Social synchronisation of ultradian behaviour cycles may also have occurred in early hominid groups.

Ultradian behaviour cycles in a village community of Colombian Indians.

The daily activities observed in a Colombian village community of contemporary hunting and gathering people were analysed with respect to their time structure. Short term cycles of about 2 hours could be detected in both individual and common behavioural patterns. These behaviour cycles of individual group members appear to have been synchronised by social interaction. From temporal variations of individual activities a common ultradian time frame emerged.

Does trampolining and anaerobic physical fitness affect sleep?

The structure of nocturnal sleep of 16 volunteers, participating in the anaerobic sports of trampolining, dancing, and soccer, was monitored by means of polygraphic recordings. Since trampolining requires the acquisition of unfamiliar patterns of motor coordination, it can be considered as a special form of motor learning, whereas the acquisition of motor skills specific for dancing and soccer can be linked with motor patterns of normal biped locomotion. According to this view, an experimental group of 8 volunteers was formed; they participated in a training course of trampolining. In addition, a control group of 8 subjects was recruited, who engaged in one of the other two anaerobic sports. Subjects who had acquired new motor skills during a 13-wk. program in trampolining showed a statistically significant increase in REM-sleep. By contrast, the 8 subjects of the control group showed no considerable changes in REM-sleep. This suggests that efforts in acquiring new and complex motor patterns activate processes specifically involved in the generation of REM stage during nocturnal sleep.

Ultradian laterality cycle in stereotyped behavior of a severely mentally retarded patient.

The stereotyped behavior of a severely mentally handicapped woman was recorded on video tape continuously during daytime. Stereotyped hand waving activity was determined separately for the right and left hands using consecutive time-sample intervals of 5 minutes. The study included 10 consecutive days and nights. During the nights EEG and eye movements were recorded polygraphically in order to score the sleep stages. Right and left-handed stereotyped activities were found to be modulated periodically with intervals of about 2 hours (ultradian cycles). During the morning and the early afternoon periodicities of both right-and left-handed activities occurred predominantly in bilateral synchrony. By contrast, rhythmic variations of both activities developed a counter-phase course during the late afternoon and evening. Specific phase relationships between the ultradian periods of stereotyped hand activities and the sleep cycle were found. These findings suggest that sleep cycle can be triggered by phases of enhanced stereotyped activity, either of left or right hand. By contrast, sleep seemed to have a synchronizing effect on ultradian cycles in stereotyped activities of both hands. Since stereotyped hand waving can be considered as manifestations of motor arousal levels of the related cerebral hemisphere, the observed periodicities can be viewed as mediated by oscillations in the bilateral brainstem arousal system. A model interpreting the main findings is proposed.