The purpose of this study was to determine the effect of visible light on the immediate pigmentation and delayed tanning of melanocompetent skin; the results were compared with those induced by long-wavelength UVA (UVA1). Two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with skin types IV-VI: UVA1 (340-400 nm) and visible light (400-700 nm). Pigmentation was assessed by visual examination, digital photography with a cross-polarized filter, and diffused reflectance spectroscopy at 7 time points over a 2-week period. Confocal microscopy and skin biopsies for histopathological examination using different stains were carried out. Irradiation was also carried out on skin type II. Results showed that although both UVA1 and visible light can induce pigmentation in skin types IV-VI, pigmentation induced by visible light was darker and more sustained. No pigmentation was observed in skin type II. The quality and quantity of pigment induced by visible light and UVA1 were different. These findings have potential implications on the management of photoaggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Recently, there has been a major thrust to understand biological processes at the nanoscale. Optical microscopy has been exceedingly useful in imaging cell microarchitecture. Characterization of cell organization at the nanoscale, however, has been stymied by the lack of practical means of cell analysis at these small scales. To address this need, we developed a microscopic spectroscopy technique, single-cell partial-wave spectroscopy (PWS), which provides insights into the statistical properties of the nanoscale architecture of biological cells beyond what conventional microscopy reveals. Coupled with the mesoscopic light transport theory, PWS quantifies the disorder strength of intracellular architecture. As an illustration of the potential of the technique, in the experiments with cell lines and an animal model of colon carcinogenesis we show that increase in the degree of disorder in cell nanoarchitecture parallels genetic events in the early stages of carcinogenesis in otherwise microscopically/histologically normal-appearing cells. These data indicate that this advance in single-cell optics represented by PWS may have significant biomedical applications.light-scattering spectroscopy ͉ nanoarchitecture ͉ subdiffusion E xisting knowledge of changes in cell architecture in disease processes is based to a large degree on the histological examination of cells and tissue. On the other hand, it is well accepted that histological and, thus, microarchitectural, aberrations are preceded by molecular, genetic, or epigenetic changes. One may pose a question whether these events are still accompanied by alterations in cell architecture that are histologically undetectable. Indeed, the diffraction limit restricts the resolution of conventional light microscopy to, at best, 200 nm. This is larger than the sizes of the fundamental building blocks of the cell, such as membranes, cytoskeleton, ribosomes, and nucleosomes. Thus, conventional light microscopy is insensitive to changes in nanoarchitecture, which is the fundamental basis of cell organization. It is clear that the fact that a cell is histologically normal may not necessarily be equated with the cell not having nanoscale structural alterations. Cellular alterations in carcinogenesis provide an illustrative and practically important example. The process of carcinoma formation involves stepwise accumulation of genetic and epigenetic alterations in epithelial cells over a time period of many years. Dysplasia, or structural alterations detectable by microscopy, is a relatively late event in this process. From a cancerresearch perspective, it is important to recognize the earlier stages of carcinogenesis that precede histological changes. One can hypothesize that although these genetic/epigenetic aberrations have not yet resulted in histologically apparent changes, they may still be accompanied by architectural consequences that occur at the nanoscale.Therefore, it is of major importance to design optical techniques for inspecting cell nanoarchitecture. One approach to...

SUMMARY Histone modifications influence higher-order chromatin structures at individual epigenomic states and chromatin environments to regulate gene expression. However, genome-wide higher-order chromatin structures shaped by different histone modifications remain poorly characterized. With stochastic optical reconstruction microscopy (STORM), we characterized the higher-order chromatin structures at their epigenomic states, categorized into three major types in interphase: histone acetylation marks form spatially segregated nanoclusters, active histone methylation marks form spatially dispersed larger nanodomains, and repressive histone methylation marks form condensed large aggregates. These distinct structural characteristics are also observed in mitotic chromosomes. Furthermore, active histone marks coincide with less compact chromatin and exhibit a higher degree of co-localization with other active marks and RNA polymerase II (RNAP II), while repressive marks coincide with densely packed chromatin and spatially distant from repressive marks and active RNAP II. Taken together, super-resolution imaging reveals three distinct chromatin structures at various epigenomic states, which may be spatially coordinated to impact transcription.

A solar-thermal water evaporation structure that can continuously generate clean water with high efficiency and good salt rejection ability under sunlight is highly desirable for water desalination, but its realization remains challenging. Here, a hierarchical solar-absorbing architecture is designed and fabricated, which comprises a 3D MXene microporous skeleton with vertically aligned MXene nanosheets, decorated with vertical arrays of metalorganic framework-derived 2D carbon nanoplates embedded with cobalt nano particles. The rational integration of three categories of photothermal materials enables broadband light absorption, efficient light to heat conversion, low heat loss, rapid water transportation behavior, and much-improved corrosion and oxidation resistance. Moreover, when assembling with a hydrophobic insulating layer with hydrophilic channel, the MXene-based solar absorber can exhibit effective inhibition of salt crystallization due to the ability to advect and diffuse concentrated salt back into the water. As a result, when irradiating under one sun, the solar-vapor conversion efficiency of the MXene-based hierarchical design can achieve up to ≈93.4%, and can remain over 91% over 100 h to generate clean vapor for stable and continuous water desalination. This strategy opens an avenue for the development of MXenebased solar absorbers for sustainable solar-driven desalination.