Forced diffusion of water molecules through aquaporin-5 biomembrane; a molecular dynamics study

Advances in Dry Eye Disease Examination Techniques

Dry eye-related ocular surface examination is very important in the diagnosis and treatment of dry eye disease. With the recent advances in science and technology, dry eye examination techniques have progressed rapidly, which has greatly improved dry eye diagnoses and treatment. However, clinically, confusion remains about which examination to choose, how to ensure the repeatability of the examination, and how to accurately interpret the examination results. In this review, we systematically evaluate previous examinations of dry eye, analyze the latest views and research hotspots, and provide a reference for the diagnosis and management of dry eye.

A novel molecular dynamics study of CO2 permeation through aquaporin-5

Aquaporins (AQPs) are protein channels which facilitate rapid water permeation across cell membrane. The AQPs are very vital for biological organs, as their malfunction causes severe diseases in human body. A particular family of AQPs, that is AQP5, has a significant role in lung fluid transport due to submucosal glands structure. However, it has not been yet well understood whether these protein channels can conduct gas molecules. Here, Molecular Dynamics (MD) simulations are used to investigate the CO₂ permeability and diffusion in AQP5 during a 40-nanosecond period. For the first time, equilibrium and Steered MD (SMD) are used to simulate self and force-induced diffusion of CO₂ molecules across AQP5 and POPE lipid bilayer. According to PMFs profile associated to CO₂ permeation, the hydrophobic central pore provides a more suitable pathway for gas molecules compared to other AQP5 channels. Although CO₂ molecules can also permeate across AQP5 water channels, the rate of CO₂ permeation through four channels of the AQP5 monomers is much lower than the central pore. The rate of CO₂ permeation through four AQP5 water channels is even lower than CO₂ diffusion through POPE lipid membrane. The results reported in this investigation demonstrate that MD simulations of human AQP5 provide valuable insights into the gas permeation mechanism for both the equilibrium self-diffusion, and quasi-equilibrium condition.

Expression of aquaporins in inner ear disease

The inner ear is responsible for hearing and balance and consists of a membranous labyrinth within a bony labyrinth. The balance structure is divided into the otolith organ that recognizes linear acceleration and the semicircular canal that is responsible for rotational movement. The cochlea is the hearing organ. The external and middle ear are covered with skin and mucosa, respectively, and the space is filled with air, whereas the inner ear is composed of endolymph and perilymph. The inner ear is a fluid-filled sensory organ composed of hair cells with cilia on the upper part of the cells that convert changes in sound energy and balance into electric energy through the hair cells to transmit signals to the auditory nerve through synapses. Aquaporins (AQPs) are a family of transmembrane proteins present in all species that can be roughly divided into three subfamilies according to structure and function: 1) classical AQP, 2) aquaglyceroporin, and 3) superaquaporin. Currently, the subfamily of mammalian species is known to include 13 AQP members (AQP0-AQP12). AQPs have a variety of functions depending on their structure and are related to inner ear diseases such as Meniere's disease, sensorineural hearing loss, and presbycusis. Additional studies on the relationship between the inner ear and AQPs may be helpful in the diagnosis and treatment of inner ear disease. Laryngoscope, 130:1532-1539, 2020.