Quantitative evaluation of macromolecular crowding environment based on translational and rotational diffusion using polarization dependent fluorescence correlation spectroscopy.

Macromolecular crowding (MMC) in cells is a hot topic in biology; therefore, well-characterized measurement standards for the evaluation of the nano-environment in MMC solutions are necessary. We propose to use polarization-dependent fluorescence correlation spectroscopy (Pol-FCS) for evaluation of macromolecular crowding in solutions. Pol-FCS can simultaneously measure the relaxation times of rotational and translational diffusion of fluorescent molecules at the same position, even in living cells with low damage. In this report, the differences in the nano-environment among solutions of small molecules, gels, and MMC solutions were evaluated by comparing their rotational and translational diffusion using Pol-FCS. Moreover, this method could distinguish the phase shift in the polyethylene glycol solution. Finally, we separately evaluated the nano-environment in the cytosol and nucleus of living cells in different cell lines and cell cycles. We expect this evaluation method to be useful in characterizing the nano-environment in MMC studies. In addition, the proposed method may be useful for other nano-environments such as liquid-liquid phase separation.

Functional Fluorescence Microscopy Imaging: Quantitative Scanning-Free Confocal Fluorescence Microscopy for the Characterization of Fast Dynamic Processes in Live Cells.

Functional fluorescence microscopy imaging (fFMI), a time-resolved (21 µs/frame) confocal fluorescence microscopy imaging technique without scanning, is developed for quantitative characterization of fast reaction-transport processes in solution and in live cells. The method is based on massively parallel fluorescence correlation spectroscopy (FCS). Simultaneous excitation of fluorescent molecules in multiple spots in the focal plane is achieved using a diffractive optical element (DOE). Fluorescence from the DOE-generated 1024 illuminated spots is detected in a confocal arrangement by a matching matrix detector comprising 32 × 32 single-photon avalanche photodiodes (SPADs). Software for data acquisition and fast auto- and cross-correlation analysis by parallel signal processing using a graphic processing unit (GPU) allows temporal autocorrelation across all pixels in the image frame in 4 s and cross-correlation between first- and second-order neighbor pixels in 45 s. We present here this quantitative, time-resolved imaging method with single-molecule sensitivity and demonstrate its usefulness for mapping in live cell location-specific differences in the concentration and translational diffusion of molecules in different subcellular compartments. In particular, we show that molecules without a specific biological function, e.g., the enhanced green fluorescent protein (eGFP), exhibit uniform diffusion. In contrast, molecules that perform specialized biological functions and bind specifically to their molecular targets show location-specific differences in their concentration and diffusion, exemplified here for two transcription factor molecules, the glucocorticoid receptor (GR) before and after nuclear translocation and the Sex combs reduced (Scr) transcription factor in the salivary gland of Drosophila ex vivo.

A comprehensive intervention following the clinical pathway of eating and swallowing disorder in the elderly with dementia: historically controlled study.

BACKGROUND: Eating problems in patients with advanced dementia are strongly associated with their deteriorating survival. Food and drink intake in people with dementia may be supported by specific interventions, but the effectiveness of such interventions is backed by almost no evidence. However, comprehensive geriatric assessment (CGA) might potentially clarify the etiology of decreased oral intake in people with dementia; thus improving their clinical outcomes. METHODS: This study was a single-arm, non-randomized trial that included historically controlled patients for comparison. We defined elderly patients with both severely decreased oral intake depending on artificial hydration and/or nutrition (AHN) and dementia as "Eating and Swallowing Disorder of the Elderly with Dementia (ESDED)". In the intervention group, participants received CGA through the original clinical pathway with multidisciplinary interventions. This was followed by individualized therapeutic interventions according to assessment of the etiology of their eating problems. RESULTS: During the intervention period (between 1st April 2013 and 31st March 2015), 102 cases of ESDED were enrolled in the study and 90 patients had completed receiving CGA. Conversely, 124 ESDED patient controls were selected from the same hospital enrolled during the historical period (between 1st April 2011 and 31st March 2012). Most participants in both groups were bedridden with severe cognitive impairment. For the intervention group, an average of 4.3 interventional strategies was recommended per participant after CGA. Serological tests, diagnostic imaging and other diagnostic examinations were much more frequently performed in the intervention group. Recovery rate from ESDED in the intervention group was significantly higher than that in the historical group (51% v.s. 34%, respectively, P = 0.02). The 1-year AHN-free survival in the intervention group was significantly higher than that in the historical group (28% v.s. 15%, respectively, P = 0.01). No significant difference between the two groups was found for 1-year overall survival (37% v.s. 28%, respectively, P = 0.08). CONCLUSIONS: Use of CGA with multidisciplinary interventions could improve the functional status of eating and allow elderly patients with severe eating problems and dementia to survive independently without the need for AHN. TRIAL REGISTRATION: ISRCTN57646445 , this trial was retrospectively registered on 8th December 2015.

Investigation of pH-dependent photophysical properties of quantum nanocrystals by fluorescence correlation spectroscopy.

Quantum dot (QD) and quantum rod (QR) nanocrystals are widely used non-organic nanocrystals. Their strong fluorescence and photostability make them suitable for biomedical imaging applications. However, their pH-dependence and antibunching properties have not been studied much, especially in aqueous conditions. In this report, we used fluorescence correlation spectroscopy (FCS) with high temporal resolution to demonstrate that the fluorescent blinking and antibunching of QDs/QRs can be changed by varying the pH of their solutions. Furthermore, herein, we reported the relationship between the aggregation and antibunching relaxation time of QDs/QRs for the first time. The findings of this study suggest that FCS can be used to discover novel environmental indicators via observing nanosecond and microsecond phenomena.

Polarization-dependent fluorescence correlation spectroscopy for studying structural properties of proteins in living cell.

Rotational diffusion measurement is predicted as an important method in cell biology because the rotational properties directly reflect molecular interactions and environment in the cell. To prove this concept, polarization-dependent fluorescence correlation spectroscopy (pol-FCS) measurements of purified fluorescent proteins were conducted in viscous solution. With the comparison between the translational and rotational diffusion coefficients obtained from pol-FCS measurements, the hydrodynamic radius of an enhanced green fluorescent protein (EGFP) was estimated as a control measurement. The orientation of oligomer EGFP in living cells was also estimated by pol-FCS and compared with Monte Carlo simulations. The results of this pol-FCS experiment indicate that this method allows an estimation of the molecular orientation using the characteristics of rotational diffusion. Further, it can be applied to analyze the degree of molecular orientation and multimerization or detection of tiny aggregation of aggregate-prone proteins.

Rotational diffusion measurements using polarization-dependent fluorescence correlation spectroscopy based on superconducting nanowire single-photon detector.

Conventional polarization-dependent fluorescence correlation spectroscopy (pol-FCS) requires two sets of photon detectors to eliminate after-pulse noises (dual-channel pol-FCS; DC-pol-FCS) in the sub-microsecond range. In this study, we successfully realized pol-FCS using a visible-wavelength superconductive nanowire single-photon detector (single-channel pol-FCS; SC-pol-FCS). The detector used is free of after-pulse noises and thus eliminates the need for dual channels in pol-FCS. Further, the optics in the SC-pol-FCS system are easier to adjust than those in the conventional system. Consequently, we obtained higher signal-to-noise ratios compared with conventional DC-pol-FCS systems. Thus, SC-pol-FCS is a potentially useful system for obtaining pol-FCS measurements, and can facilitate improved rotational diffusion studies.