Molecular Frontiers Journal

We report on progress in observing the hydrogen-bonded structure of water and sea water by deep-ocean Raman spectroscopy. In the normal ocean, the abundance of single H₂O species is less than 20%. The principal form is the tetrahedral pentamer, and the (H₂O)${}_{\text{n}}\leftrightarrow$ nH₂O equilibrium plays a dominant role in controlling physicochemical processes and the speed of sound. The enthalpy of the H-bond in water is 2.624 kcal/mol, and in sea water 2.258 kcal/mol due to the quantity of non-HB water in the solvation shell of sea salt ions. The activation energy of viscous flow is 4.28 kcal/mol at one atmosphere pressure, consistent with the need to break hydrogen bonds and overcome the van der Waals intermolecular forces. The activation energy decreases exponentially with depth/pressure and is 10% less at 4,000 m depth. We suggest this is due to the pressure-induced shift in the water equilibrium to favor the less compressible quasi-planar pentamer, tetramer, and so on forms. We address the long-standing conclusion that microbial swimming by means of rotating flagella is only 1%–2% efficient. This neglects the need for microbes to overcome the activation energy of viscous flow; $\sim$95% of the mechanical energy produced by the flagella must be used to break H-bonds and overcome intermolecular forces.

The synthetic scalability of water harvesting metal–organic frameworks (MOFs) is crucial for making these promising materials accessible and widely available for use in household devices. Herein, we present a facile, sustainable, and high-yield synthesis method to produce a series of water-harvesting MOFs, including MOF-303, CAU-23, MIL-160, MOF-313, CAU-10, and Al-fumarate. Using readily available reactants and water as the only solvent, we were able to synthesize these materials at the kilogram scale in a 200 L batch reactor with yields of 84–96% and space-time yields of 238–305 kg/day/m³ under optimized reaction conditions. We also show that our procedure preserves framework crystallinity, porosity, and water-harvesting performance of the MOFs synthesized at scale.

Changing climate threatens our water systems: Droughts, fires, and floods disrupt access to safe water and no country is immune. The aging infrastructure crisis offers an opportunity to build resiliency into our future water systems with approaches like (non-)potable reuse. Such strategies require participation by end-users, which we propose can be championed by water utilities through: (1) Raising awareness of water challenges, (2) education about current water realities and opportunities, and (3) providing resources to implement and sustain water solutions.

Four properties define exosomes. First, they are tiny bodies–as small as 35 nm in diameter, 1,000 times less than the width of a human hair—that perform key assignments in cell signaling and other biological processes. Second, their size aids in transiting hard-to-navigate tissue boundaries in the body, such as the brain–blood barrier and the gut–blood barrier, optioning an oral administration of therapy in some instances. Third, since they can convey protein peptides, nucleic acids, and small molecule drugs, they represent an amalgam of proteomic, genomic, and lipidomic concepts in biomedicine. And fourth, it is conceivable, exosomes can address any human disease—many of which cannot be accessed today—even using material from other species. Two research groups—in St. Louis and Montreal—first characterized them almost simultaneously in 1984, offering an explanation of how immature red blood cells lost their iron-transporting transferrin receptor when they matured. Their role as intercellular communicators grew in 1996 when researchers at the University of Utrecht showed how exosomes induced a powerful immune response that caused cancerous tumors to regress. They travel in every body fluid: blood, lymph, urine, tears, saliva, cerebrospinal, and mother’s milk. Originally seen in electron micrographs and thought to be inconsequential, they now have a presence in biotechnology as a new platform for diagnostics and therapy, broadly representing proteome medicine. As yet, they have not reached a critical mass for clinical adoption, though their prospects are tantalizing. This piece ends with a prediction—that by 2034, the 50th anniversary of the term exosome, proteome medicine will have several generally recognized as safe and effective exosome-based prescriptions, with China leading the way.

Exosomes are the small extracellular vesicles secreted by almost all living cell types. They are a main component of cellular communication. To mediate intercellular communication, exosomes transport cellular cargo such as proteins, miRNA, nucleic acids, and various metabolites${}^{21}$. Although specifics of their role in cellular physiology have yet to be uncovered, interest in exosomes and their functionality has exploded due to their diverse treatment and diagnostic capabilities. Already, numerous studies have proven the safety, efficacy, and therapeutic potential of exosomes in the treatment of cancers, neurodegenerative disorders, cardiovascular illness, and orthopedic diseases¹. Due to their small size, high membrane permeability, and modifiability, exosomes are of the utmost therapeutic and diagnostic potential${}^{21}$. As exosomes promote cellular regeneration, their role in general dermatology as well as cosmetic dermatology has become prominent. In the past few years, cosmetic dermatology research proves the potential of exosomes in the processes of skin rejuvenation, postprocedural care, and dermal maintenance. Some of the most popular modalities of treatment include hair restoration, photorejuvenation, daily maintenance, and antiaging. This paper will discuss the biological function, isolation methods, and therapeutic role of mesenchymal stem cell-and platelet-derived exosomes in cosmetic dermatology.

Helices are ubiquitous in art and nature. Independent of their pitch and sense of rotation (handedness), helices in sculpture, painting, architecture, scientific illustrations, conference announcements, logos, and advertising are eye-catching and aesthetically pleasing. Helices can turn either clockwise (right-handed helix) or anti-clockwise (left-handed helix). The $\alpha$-helix formed by l-amino acids and the double helices formed by $\beta$-d-2^′-deoxyribonucleic acid (A- and B-form DNA) and $\beta$-d-ribonucleic acid (A-form RNA) are all right-handed. Artistic license provides the freedom to create helices of any shape and sense; indeed, many helical sculptures do not follow the natural convention observed in proteins and DNA. What is more surprising, given that models of the $\alpha$-helix and the DNA double helix were published over 70 years ago, is how common left-handed DNA double helices are in the context of scientific papers and books as well as in popular science writing and reporting. In all cases except for left-handed Z-DNA, the use of left-handed helices in scientific illustrations or models is incorrect. Here, we revisit the helix types adopted by peptides, DNA, and RNA, and review examples of right and wrong helical models in science, art, and elsewhere.