Thermal Analysis of Bacterial Ribosomes

Ribosomal particles of E. coli were examined by using a heat leakage scanning calorimeter. Remarkable changes were observed in thermograms of 70S ribosomes and their subunits when the Mg²⁺ concentration was raised from 1 mm to 10 mm. It was suggested that ribosomal subunits exist in more than one conformation, and changes in their conformation might be the primary cause of the association-dissociation process of ribosomes. Comparisons of thermograms of RNase- and chymotrypsin-treated, as well as non-treated SOS and 30S subunits suggest that conformational changes in each subunit may be ascribed to changes in rRNA.     

Breakage of Chromosomal DNA with Aromatic Reductones

Strand breakages of mammalian cellular chromosomal DNA with aromatic reductones were ascertained by use of a cultured cell strain of the rat fetal lung (RFL). The mode of the breakages was investigated by ultracentrifugal analyses. The reductones induced the breakages of the cellular DNA in two different fashions; one is single strand breaks and another double strand breaks. Although the single strand breaks were rapidly repaired, double strand breaks were only partially repaired. Both breaks were not cytocidal. Some physiological alterations were observed to follow the strand breaks.     

Psychological and physiological effect in humans of touching plant foliage - using the semantic differential method and cerebral activity as indicators

Background

Numerous studies have reported on the healing powers of plants and nature, but there have not been so many instances of experimental research. In particular, there are very few psychological and physiological studies using tactile stimuli. This study examines the psychological and physiological effects of touching plant foliage by using an evaluation profile of the subjects’ impressions and investigating cerebral blood flow.

Methods

The subjects were 14 young Japanese men aged from 21 to 27 years (mean ± standard deviation: 23.6 ± 2.4). With their eyes closed, the subjects touched four different tactile samples including a leaf of natural pothos (Epipremnum aureum). The physiological indices were compared before and after each stimulus. Psychological indices were obtained using a ‘semantic differential’ method.

Results

The fabric stimulus gave people ‘soft’ and ‘rough’ impressions, ‘kind’, ‘peaceful’ and ‘pleasant’ feelings psychologically, and a sense of physiological calm. On the other hand, the metal stimulus gave people ‘cold’, ‘smooth’ and ‘hard’ impressions and an image of something ‘artificial’. The metal stimulus caused a stress response in human cerebral blood flow although its evaluation in terms of ‘pleasant or unpleasant’ was neutral. There were no remarkable differences between the stimuli of natural and artificial pothos compared with other types of stimulus psychologically. However, only the natural pothos stimulus showed a sense of physiological calm in the same appearance as the fabric stimulus.

Conclusions

This study shows that people experience an unconscious calming reaction to touching a plant. It is to be concluded that plants are an indispensable element of the human environment.     

Late circadian phase in adults and children is correlated with use of high color temperature light at home at night

Light is the strongest synchronizer of human circadian rhythms, and exposure to residential light at night reportedly causes a delay of circadian rhythms. The present study was conducted to investigate the association between color temperature of light at home and circadian phase of salivary melatonin in adults and children. Twenty healthy children (mean age: 9.7 year) and 17 of their parents (mean age: 41.9 years) participated in the experiment. Circadian phase assessments were made with dim light melatonin onset (DLMO). There were large individual variations in DLMO both in adults and children. The average DLMO in adults and in children were 21:50 ± 1:12 and 20:55 ± 0:44, respectively. The average illuminance and color temperature of light at eye level were 139.6 ± 82.7 lx and 3862.0 ± 965.6 K, respectively. There were significant correlations between color temperature of light and DLMO in adults (r = 0.735, p < 0.01) and children (r = 0.479, p < 0.05), although no significant correlations were found between illuminance level and DLMO. The results suggest that high color temperature light at home might be a cause of the delay of circadian phase in adults and children.     

Water-soluble ferulic acid derivatives improve amyloid-β-induced neuronal cell death and dysmnesia through inhibition of amyloid-β aggregation

Ferulic acid (FA) has been reported to exhibit protective effects against amyloid-β (Aβ)-induced neurodegeneration in vitro and in vivo. Recently, we developed two water-soluble FA derivatives: 1-feruloyl glycerol and 1-feruloyl diglycerol. In this study, we examined the neuroprotective effects of these water-soluble FA derivatives on Aβ-induced neurodegeneration both in vitro and in vivo. FA and water-soluble FA derivatives inhibited Aβ aggregation and destabilized pre-aggregated Aβ to a similar extent. Furthermore, water-soluble FA derivatives, as well as FA, inhibited Aβ-induced neuronal cell death in cultured neuronal cells. In in vivo experiments, oral administration of water-soluble FA derivatives to mice improved Aβ-induced dysmnesia assessed by contextual fear conditioning test and protected hippocampal neurons against Aβ-induced neurotoxicity. This study provides useful evidence suggesting that water-soluble FA derivatives are expected to be effective neuroprotective agents.     

How Japanese anchovy spawn in northern waters: start with surface warming and end with day length shortening

Ichthyological Research - Concordant with stock increase, Japanese anchovy Engraulis japonicus seems to expand its spawning ground northward from subtropical waters along the Kuroshio Current to...     

Crystal structure of unautoprocessed precursor of subtilisin from a hyperthermophilic archaeon: evidence for Ca2+-induced folding

The crystal structure of an active site mutant of pro-Tk-subtilisin (pro-S324A) from the hyperthermophilic archaeon Thermococcus kodakaraensis was determined at 2.3 A resolution. The overall structure of this protein is similar to those of bacterial subtilisin-propeptide complexes, except that the peptide bond linking the propeptide and mature domain contacts with the active site, and the mature domain contains six Ca2+ binding sites. The Ca-1 site is conserved in bacterial subtilisins but is formed prior to autoprocessing, unlike the corresponding sites of bacterial subtilisins. All other Ca2+-binding sites are unique in the pro-S324A structure and are located at the surface loops. Four of them apparently contribute to the stability of the central alphabetaalpha substructure of the mature domain. The CD spectra, 1-anilino-8-naphthalenesulfonic acid fluorescence spectra, and sensitivities to chymotryptic digestion of this protein indicate that the conformation of pro-S324A is changed from an unstable molten globule-like structure to a stable native one upon Ca2+ binding. Another active site mutant, pro-S324C, was shown to be autoprocessed to form a propeptide-mature domain complex in the presence of Ca2+. The CD spectra of this protein indicate that the structure of pro-S324C is changed upon Ca2+ binding like pro-S324A but is not seriously changed upon subsequent autoprocessing. These results suggest that the maturation process of Tk-subtilisin is different from that of bacterial subtilisins in terms of the requirement of Ca2+ for folding of the mature domain and completion of the folding process prior to autoprocessing.     

Structure of the antitumour enzyme L-methionine gamma-lyase from Pseudomonas putida at 1.8 A resolution

l-Methionine gamma-lyase (EC 4.4.1.11, MGL_Pp) from Pseudomonas putida is a multifunctional enzyme, which belongs to the gamma-family of pyridoxal-5'-phosphate (PLP) dependent enzymes. In this report, we demonstrate that the three-dimensional structure of MGL_Pp has been completely solved by the molecular replacement method to an R-factor of 20.4% at 1.8 A resolution. Detailed information of the overall structure of MGL_Pp supplies a clear picture of the substrate- and PLP-binding pockets. Tyr59 and Arg61 of neighbouring subunits, which are strongly conserved in other gamma-family enzymes, contact the phosphate group of PLP. These residues are important as the main anchor within the active site. Lys240, Asp241 and Arg61 of one partner monomer and Tyr114 and Cys116 of the other partner monomer form a hydrogen-bond network in the MGL active site which is specific for MGLs. It is also suggested that electrostatic interactions at the subunit interface are involved in the stabilization of the structural conformation. The detailed structure will facilitate the development of MGL_Pp as an anticancer drug.     

Protein thermostabilization requires a fine-tuned placement of surface-charged residues

Using the information from the genome projects, recent comparative studies of thermostable proteins have revealed a certain trend of amino acid composition in which polar residues are scarce and charged residues are rich on the protein surface. To clarify experimentally the effect of the amino acid composition of surface residues on the thermostability of Escherichia coli Ribonuclease HI (RNase HI), we constructed six variants in which five to eleven polar residues were replaced by charged residues (5C, 7Ca, 7Cb, 9Ca, 9Cb and 11C). The thermal denaturation experiments indicated that all of the variant proteins are 3.2-10.1 degrees C in Tm less stable than the wild proteins. The crystal structures of resultant protein variants 7Ca, 7Cb, 9Ca and 11C closely resemble that of E. coli RNase HI in their global fold, and several different hydrogen bonding and ion-pair interactions are formed by the mutations. Comparison of the crystal structures of these variant proteins with that of E. coli RNase HI reveals that thermal destabilization is apparently related to electrostatic repulsion of the charged residues with neighbours. This result suggests that charged residues of natural thermostable proteins are strictly posted on the surface with optimal interactions and without repulsive interactions.     

Inhibition of heart rate variability during sleep in humans by 6700 K pre-sleep light exposure

Two different spectral analyses of heart rate (HR) variability (HRV) were performed on seven young male subjects to evaluate the effects of different color temperatures of light exposure (6700 K, 5000 K, 3000 K) before sleep on cardiac vagal activity. In investigating HRV, we used an ordinary fast Fourier transform (FFT) and coarse graining spectral analysis (CGSA), which selectively extracts random fractal components from a given time series. The results showed that suppressions of HR during sleep after 6700 K light exposure were more inhibited than the other two lighting conditions. Increases in high-frequency (HF) components of HRV during sleep were also inhibited by 6700 K pre-sleep lighting. These results indicate that pre-sleep exposure to light of a higher color temperature may inhibit the enhancement of cardiac vagal activity during sleep. Moreover, significant HF alterations were shown in fractal-free HF (not in ordinary HF) components by CGSA. Because the HF component originates from respiratory sinus arrhythmia with periodical fluctuations, CGSA may be an appropriate approach for HRV evaluation during sleep.