Chemistry News

Hand-Held AO Ophthalmoscopy Enables Cellular-Level Imaging

posted Nov 16, 2018, 7:39 AM by ­김형민‎(응용화학과)‎

Advancements in adaptive optics and ophthalmic imaging are facilitating the visualization of the
human retina and providing researchers with an expanded understanding of eye health and disease.
AO was first used in astronomical telescopes to reduce wavefront distortions induced by atmospheric turbulence. Its applications have expanded to find utility in ophthalmic imaging, high-power lasers, vision research, and microscopy.

Concentration Quenching in Upconversion Nanocrystals

posted Nov 16, 2018, 7:16 AM by ­김형민‎(응용화학과)‎

Despite considerable effort to improve upconversion (UC) in lanthanide-doped nanocrystals (NCs), the maximum reported efficiencies remain below 10%. Recently, we reported on low Er3+- and Yb3+-doped NaYF4 NCs giving insight into fundamental processes involved in quenching for isolated ions. In practice, high dopant concentrations are required and there is a trend toward bright UC in highly doped NCs. Here, additional quenching processes due to energy transfer and migration add to a reduction in UC efficiency. However, a fundamental understanding on how concentration quenching affects the quantum efficiency is lacking. Here, we report a systematic investigation on concentration-dependent decay dynamics for Er3+ or Yb3+ doped at various concentrations (1−100%) in core and core−shell NaYF4 NCs. The qualitative and quantitative analyses of luminescence decay curves and emission spectra show strong concentration quenching for the green emitting Er3+ 4S3/2 and NIR-emitting 4I11/2 levels, whereas concentration quenching for the red-emitting 4F9/2 level and the IR emitting 4I13/2 level is limited. The NIR emission of Yb3+ remains efficient even at concentration as high as 60% Yb3+, especially in core−shell NCs. Finally, the role of solvent quenching was investigated and reveals a much stronger quenching in aqueous media that can be explained by the high-energy O−H vibrations. The present study uncovers a more complete picture of quenching processes in highly doped UC NCs and serves to identify methods to further optimize the efficiency by careful tuning of lanthanide concentrations and core−shell design.


posted Oct 18, 2018, 7:18 AM by ­김형민‎(응용화학과)‎

A Total of $22 Million Awarded for Breakthroughs in Treatment for the Leading Genetic Cause of Infant Death, Super-Resolution Imaging, Discovery of a New Kind of Electronic Material, and Other Major Achievements. 
2019 Breakthrough Prize in Life Sciences Awarded to C. Frank Bennett and Adrian R. Krainer, Angelika Amon, Xiaowei Zhuang, and Zhijian “James” Chen. 
2019 Breakthrough Prize in Fundamental Physics Awarded to Charles Kane and Eugene Mele.
2019 Breakthrough Prize in Mathematics Awarded to Vincent Lafforgue. 
Six “New Horizons” Prizes Worth $600,000 Awarded for Early-Career Achievement in Physics and Math. 

Simultaneous, noninvasive observation of elastic scattering, fluorescence and inelastic scattering as a monitor of blood flow and hematocrit in human fingertip capillary beds

posted Oct 12, 2018, 10:29 AM by ­김형민‎(응용화학과)‎

J. of Biomedical Optics, 14(5), 050505 (2009).

We report simultaneous observation of elastic scattering, fluorescence, and inelastic scattering from in vivo near-infrared probing of human skin. Careful control of the mechanical force needed to obtain reliable registration of in vivo tissue with an appropriate optical system allows reproducible observation of blood flow in capillary beds of human volar side fingertips. The time dependence of the elastically scattered light is highly correlated with that of the combined fluorescence and Raman scattered light. We interpret this in terms of turbidity (the impeding effect of red blood cells on optical propagation to and from the scattering centers) and the changes in the volume percentages of the tissues in the irradiated volume with normal homeostatic processes. By fitting to a model, these measurements may be used to determine volume fractions of plasma and RBCs.

Biological applications of anti-stokes Raman spectroscopy: quantitative analysis of glucose in plasma and serum by a highly sensitive multichannel Raman spectrometer

posted Oct 12, 2018, 10:27 AM by ­김형민‎(응용화학과)‎

This study demonstrates the potential of anti-Stokes Raman spectroscopy in investigating biological samples in a nondestructive manner; quantitative analysis of glucose in plasma and serum has been studied as an example. The efficient collection of anti-Stokes Raman scattering by use of chromatic aberration of a lens has allowed us to obtain high-quality anti-Stokes Raman spectra from glucose in plasma and serum, which is a strongly fluorescent biological sample. The concentration of glucose in these materials can be estimated by the anti-Stokes Raman intensity of the band at 1130 cm<sup>-1</sup> due to the C-O stretching mode. The correlation coefficient between the concentration and the intensity has been calculated to be 0.993 and 0.991 for glucose in plasma and serum, respectively. The detection limits for these materials have been found to be 45 mg/dL and 50 mg/dL, respectively.

The best supervisor

posted Oct 12, 2018, 7:07 AM by ­김형민‎(응용화학과)‎

A PhD is hard. But a good supervisor makes it much easier.

My PhD supervisor died in June. I’d met with him only days earlier so that he could painstakingly revise my manuscript, giving me several hours of his precious time. He had a way of asking the very questions I didn’t want to answer, highlighting the limitations of my work that I’d been trying to hide or skim over. “You need evidence,” he’d claim, jabbing a forefinger at one of my many ‘unsubstantiated assertions’. He hated those. But he loved a good reference — although not too many for each assertion, mind you.

Role of University

posted Oct 12, 2018, 6:53 AM by ­김형민‎(응용화학과)‎   [ updated Oct 12, 2018, 7:16 AM ]

What is the MIT $100K?

One competition - three independent contests - from October through May. Now in its 30th year, the MIT $100K Entrepreneurship Competition has brought together students and researchers from across MIT and Greater Boston to launch their talent, ideas, and technology into leading companies. 

The competition runs as series of distinct, increasingly intensive contests: Pitch, Accelerate, and Launch.

Each contest focuses on developing specific founder skills. For semi-finalists in Accelerate and Pitch, the MIT $100K brings together a network of resources, including mentorship from venture capitalists, serial entrepreneurs, corporate executives, and attorneys; media exposure; prototyping funds; business plan feedback; and discounted services. More than $300K in non-dilutive funding is awarded to accelerate these new ventures.

Department career expo

This Biological Engineering Career Expo takes place in the Samberg Conference Center at MIT in two adjoining rooms to provide maximum flexibility for combined recruiting of undergraduate and PhD-level candidates. One room accommodates tables for company displays and is the primary venue for recruiting BS-level students. 
The other room is to have company tables and PhD research posters. PhD-level candidates will present posters from 2pm – 4:45 pm. MIT BE faculty are invited to attend the poster session. BS-level candidates will be invited to visit the displays 3 – 4:45 pm. This arrangement allows maximum flexibility for companies recruiting at both BS and PhD levels, especially with multiple recruiters. The event can accommodate up to 6 recruiters per company. 

*Note: Resumes submitted by Friday 10/12 at midnight will be compiled and sent to companies. Printed nametags will also be made available for those who register before this deadline.

Universities fund off-the-wall research from their own pockets

The competition to secure funding can deter applicants from submitting radical research proposals, despite their potential for dramatic advance. At University College London (UCL), we have been running a programme for ten years that bypasses conventional funding mechanisms, using our own resources to open up new and unpredictable lines of enquiry. A grant-application system such as that used today would probably have denied support to many of the twentieth-century scientists who fundamentally changed the ways we think. For example, molecular biologist Oswald Avery and his colleagues disproved the widely held belief that the genetic molecule was a protein (O. T. Avery et al. J. Exp. Med. 79, 137–158; 1944). UCL took its lead from British Petroleum’s Venture Research Unit (1980–93), which awarded funding to a handful of applicants with radical ideas — simply on the basis of face-to-face discussion. Despite vetoes by peer reviewers, the unit supported academics such as Ken Seddon, who became the United Kingdom’s most cited chemist for his work on ionic liquids, and Steve Davies, who set up a company to further his research into molecular architecture and chiral selection. The company sold in 2000 for £316 million (then about US$200 million) — some 15 times the unit’s total outlay on venture research. Universities should follow UCL’s lead and use their own resources to set up similar initiatives.

Is Raman Optical Activity Spectroscopy Sensitive to beta‐turns in Proteins? Secondary Structure and Side‐Chain Dependence

posted Sep 17, 2018, 8:55 AM by ­김형민‎(응용화학과)‎

β‐turns are essential for the structure and function of proteins. The spectroscopic technique Raman optical activity (ROA) has been suggested to be sensitive to such structural elements of proteins in solution. Three spectral features have been reported to mark β‐turns in protein ROA spectra: being a negative band at 1220 cm‐1, positive intensity around 1290 cm‐1 and negative intensity around 1340‐1380 cm‐1. In this work, density functional theory calculations demonstrated that these assignments are inaccurate as these spectral regions are not robust and sense the exact secondary structure surrounding the β‐turn as well. Furthermore, it was demonstrated that the amino acid side‐chains affect the exact ROA patterns which can direct future research to perform a systematic analysis of the contributions of the side‐chains.

Multi-photon near-infrared emission saturation nanoscopy using upconversion nanoparticles

posted Sep 17, 2018, 8:49 AM by ­김형민‎(응용화학과)‎

Nature Communicationsvolume 9, Article number: 3290 (2018)

Multiphoton fluorescence microscopy (MPM), using near infrared excitation light, provides increased penetration depth, decreased detection background, and reduced phototoxicity. Using stimulated emission depletion (STED) approach, MPM can bypass the diffraction limitation, but it requires both spatial alignment and temporal synchronization of high power (femtosecond) lasers, which is limited by the inefficiency of the probes. Here, we report that upconversion nanoparticles (UCNPs) can unlock a new mode of near-infrared emission saturation (NIRES) nanoscopy for deep tissue super-resolution imaging with excitation intensity several orders of magnitude lower than that required by conventional MPM dyes. Using a doughnut beam excitation from a 980 nm diode laser and detecting at 800 nm, we achieve a resolution of sub 50 nm, 1/20th of the excitation wavelength, in imaging of single UCNP through 93 μm thick liver tissue. This method offers a simple solution for deep tissue super resolution imaging and single molecule tracking.

High efficiency upconversion nanophosphors for high-contrast bioimaging

posted Aug 29, 2018, 9:43 PM by ­박수빈‎[응용화학과]‎

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