Biology subjects

Kamimura, T.

Publications and source records attributed to Kamimura, T..

3 recordsLinked to original sources

bioRxiv2024

Protonation/deprotonation-driven switch for the redox stability of low-potential ferredoxin

Ferredoxin is a small iron-sulfur protein and acts as an electron carrier. Low-potential ferredoxins harbor [4Fe-4S] cluster(s), which play(s) a crucial role as the redox center. Low-potential ferredoxins are able to cover a wide range of redox potentials (-700 to -200 mV); however, the mechanisms underlying the factors which control the redox potential are still enigmatic. Here, we determined the neutron structure of ferredoxin from Bacillus thermoproteolyticus, and experimentally revealed the exact hydrogen-bonding network involving the [4Fe-4S] cluster. The density functional theory calculations based on the hydrogen-bonding network revealed that protonation states of the sidechain of Asp64 close to the [4Fe-4S] cluster critically affected the stability of the reduced state in the cluster. These findings provide the first identification of the intrinsic control factor of redox potential for the [4Fe-4S] cluster in low-potential ferredoxins.

biochemistry↗

bioRxiv2020

Tongue thickness measured by ultrasonography is associated with tongue pressure in the Japanese elderly

The term "oral frailty" reflects the fact that oral health is associated with physical frailty and mortality. Tongue thickness measurement is one of the evaluations for swallowing function. The aim of this study was to investigate the relationship between tongue thickness and tongue pressure in the Japanese elderly. We evaluated 254 elderly patients; all the participants underwent tongue ultrasonography and tongue pressure measurement. To determine tongue thickness, we measured the vertical distance from the surface of the mylohyoid muscle to the tongue dorsum using ultrasonography. Result analyses revealed that tongue thickness was linearly associated with tongue pressure in both sexes. In male participants, dyslipidemia, lower leg circumference, and tongue pressure were independently significantly associated with tongue thickness. In female participants, body mass index and tongue pressure were independently significantly associated with tongue thickness. Tongue thickness was significantly decreased by age for both men and women. The optimal cutoff for tongue thickness to predict the tongue pressure of < 20 kPa was 41.3 mm in males, and 39.3 mm in females. In the Japanese elderly, tongue thickness using ultrasonography is associated with tongue pressure. Tongue thickness and tongue pressure, which are sensitive markers for oral frailty, decrease in aging. The tongue ultrasonography provides a less invasive technique for determining tongue thickness and related aspiration risks for elderly patients.

neuroscience↗

bioRxiv2020

Dynamical determinants of different spine movements and gait speeds in rotary and transverse gallops

Quadruped gallop is categorized into two types: rotary and transverse. While the rotary gallop involves two types of flight with different spine movements, the transverse gallop involves only one type of flight. The rotary gallop can achieve faster locomotion than the transverse gallop. To clarify these mechanisms from a dynamic viewpoint, we developed a simple model and derived periodic solutions by focusing on cheetahs and horses. The solutions gave a criterion to determine the flight type: while the ground reaction force does not change the direction of the spine movement for the rotary gallop, it changes for the transverse gallop, which was verified with the help of animal data. Furthermore, the criterion provided the mechanism by which the rotary gallop achieves higher-speed than the transverse gallop based on the flight duration. These findings improve our understanding of the mechanisms underlying different gaits that animals use.

bioinformatics↗