Comment on "Orientational Distribution of Free O-H Groups of Interfacial Water is Exponential"

In a recent letter (PRL,121,246101,2018), Sun et al. reported that combined MD simulation and sum frequency generation vibrational spectroscopy (SFG-VS) measurements led to conclusions of a broad and exponentially decaying orientational distribution, and the presence of the free O-H group pointing down to the bulk at the air/water interface. In this comment, we show that their main conclusions are based on questionable interpretation of the SFG-VS data presented in the letter [1], and are also contrary to the established data analysis and interpretations in the literature [2-5].Comment: 2 pages, 0 figure

Spectroscopic Evidence for the Specific Na+ and K+ Interactions with the Hydrogen-bonded Water Molecules at the Electrolyte Aqueous Solution Surfaces

Sum frequency generation vibrational spectra of the water molecules at the NaF and KF aqueous solution surfaces showed significantly different spectral features and different concentration dependence. This result is the first direct observation of the cation effects of the simple alkali cations, which have been believed to be depleted from the aqueous surface, on the hydrogen bonding structure of the water molecules at the electrolyte solution surfaces. These observations may provide important clue to understand the fundamental phenomenon of ions at the air/water interface.Comment: 15 pages, 2 figure

Innate Immune Defense in the Male Reproductive System and Male Fertility

To protect the male germ cells from adverse immune reaction, the male reproductive system adopts special immune environment such as immunoprivileged status. The male genital organs can be infected by various microorganisms via hematogenous dissemination and ascending genitourinary tracts. To overcome the immunoprivileged status, the male genital organs also adopt their own innate defense against microbial infection. The tissue-specific cells in the male reproductive system are well equipped with innate immune machineries, including pattern recognition receptors (PRRs) and their negatively regulatory system. PRR-initiated immune responses must be tightly regulated by the negative regulatory system for the maintenance of immune homeostasis. The immune homeostasis can be disrupted by unrestrictive innate immune response, which may lead to inflammatory conditions in the male genital tracts, an important etiological factor contributing to male infertility. This chapter describes the current understanding of the innate immune responses in the male reproductive system and their effects on male fertility