@article{li_lim_puretzky_long_riehn_hallen_2018, title={DNA methylation detection using UV nano bowtie antenna enhanced Raman spectroscopy}, volume={10727}, ISSN={["1996-756X"]}, DOI={10.1117/12.2321283}, abstractNote={Methylation in DNA is a controlling factor in gene expression, embryonic development, and has been found to be important in infections and cancer. From a basic biology point of view, great heterogeneity has been found in methylation levels within tissues, so questions arises as to how and why. We show that methylated-DNA (m-DNA) can be distinguished from non-methylated (n-DNA) with nano-bowtie- and resonance- enhanced Raman spectra. By tuning the bowtie antenna to the resonance wavelength, both gains can be realized. Two additional Raman peaks in the 1200 – 1700 cm-1 band appear with methylation: one at 1239 cm-1 and the other at 1639 cm-1; a weak peak near 1000 cm-1 also appears with methylation. We also find that the two spectral features, although the latter with slight modification, can be used to distinguish the methylation state even when the DNA is denatured, as we show when we induce crystallization of the salts in the solution with increased excitation power, or allow it to happen naturally via solvent evaporation, and the DNA is trapped within the salt crystals. A comparison between liquid/solution to dried/denatured state m-DNA shows a general broadening of the larger lines and a transfer of spectral weight from the ~1470 cm-1 vibration to two higher energy lines. The applicability of the resonance-Raman in these spectra is shown by demonstrating that the Raman spectral characteristics hardly change as the Raman resonance in excitation wavelength is approached. Finally, we comment on real signal gain in this double-resonance system.}, journal={UV AND HIGHER ENERGY PHOTONICS: FROM MATERIALS TO APPLICATIONS 2018}, author={Li, Ling and Lim, Shuang Fang and Puretzky, Alexander and Long, Brandon J. N. and Riehn, Robert and Hallen, Hans}, year={2018} }
 @article{long_zheng_schweitzer_hallen_2018, title={Resonance Raman Imagery of Semi-Fossilized Soft Tissues}, volume={10753}, ISSN={["1996-756X"]}, DOI={10.1117/12.2321298}, abstractNote={The discovery of soft structures in dinosaur bone with the morphological and molecular characteristics of blood vessels in extant vertebrates was both surprising and controversial. Mounting evidence suggests that these soft tissues are blood vessels, their preservation driven in part by reactive oxygen species derived from hemoglobin degradation. More data are needed to support this hypothesis. Raman spectroscopy, and resonance Raman in particular, can provide detailed information as to the chemical makeup of these samples. We used two different excitation wavelengths in microscale Raman measurements to look for lines characteristic of degraded heme molecules, both in ancient vessels and modern analogues taken from semi-fossilized, hemoglobin-soaked ostrich bones. In both samples, we observed two regimes: dark colored, stiff regions and more transparent, elastic regions. We discovered that the two apparent regimes in the samples had different strengths of Raman returns, and that resonance effects greatly affected the Raman intensity. In all cases, there was some evidence of degraded heme spectra, though the increased returns indicated that the dark regimes had reacted more strongly with the heme specie. The modern vessels displayed a resonance Raman intensity consistent with hemoglobin molecular structures, which indicated resonance spectra would provide understanding of the ancient heme molecule. To investigate the two regimes more thoroughly, we acquired Raman spectra over areas where the sample transitioned from one regime to another. Variable wavelength resonance Raman measurements over the whole sample were used to give more information about the heme species present, in both ancient and modern samples.}, journal={ULTRAFAST NONLINEAR IMAGING AND SPECTROSCOPY VI}, author={Long, Brandon and Zheng, Wenxia and Schweitzer, Mary and Hallen, Hans}, year={2018} }
 @inproceedings{hallen_long_hook_pangle_philbrick_2013, title={Multistatic lidar measurements of non-spherical aerosols}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Hallen, H. D. and Long, B. J. N. and Hook, D. A. and Pangle, G. E. and Philbrick, C. R.}, year={2013} }
 @inproceedings{pangle_hook_long_philbrick_hallen_2013, title={Optical extinction dependence on wavelength and size distribution of airborne dust}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Pangle, G. E. and Hook, D. A. and Long, B. J. N. and Philbrick, C. R. and Hallen, H. D.}, year={2013} }
 @inproceedings{hook_pangle_long_philbrick_hallen_2013, title={Understanding lidar returns from complex dust mixtures}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Hook, D. A. and Pangle, G. E. and Long, B. J. N. and Philbrick, C. R. and Hallen, H. D.}, year={2013} }
 @inproceedings{long_hook_pangle_hallen_philbrick_2013, title={Using a laser aureole to study aerosols}, volume={8731}, booktitle={Laser radar technology and applications xviii}, author={Long, B. J. N. and Hook, D. A. and Pangle, G. E. and Hallen, H. D. and Philbrick, C. R.}, year={2013} }