Yuanlong Yang

Torsional Vibrational Modes of Tryptophan Studied by Terahertz Time-Domain Spectroscopy

The low-frequency torsional modes, index of refraction, and absorption of a tryptophan film and pressed powders from 0.2 to 2.0 THz (6.6-66 cm(-1)) were measured by terahertz time-domain spectroscopy at room temperature. It was found that there were two dominated torsional vibrational modes at around 1.435 and 1.842 THz. The associated relaxation lifetimes ( approximately 1 ps) for these modes of the tryptophan molecule were measured. Using a density-functional calculation, the origins of the observed torsional vibrations were assigned to the chain and ring of the tryptophan molecule.

Native fluorescence spectra of human cancerous and normal breast tissues analyzed with non-negative constraint methods

The native fluorescence spectra of human cancerous and normal breast tissues were investigated using the selected excitation wavelength of 340 nm to excite key building block molecules, such as reduced nicotinamide adenine dinucleotide (NADH), collagen, and flavin. The measured emission spectra were analyzed using a non-negative constraint method, namely multivariate curve resolution with alternating least-squares (MCR-ALS). The results indicate that the biochemical changes of tissue can be exposed by native fluorescence spectra analysis. The MCR-ALS-extracted components corresponding to the key fluorophores in breast tissue, such as collagen, NADH, and flavin, show differences of relative contents of fluorophores in cancerous and normal breast tissues. This research demonstrates that the native fluorescence spectroscopy measurements are effective for detecting changes of fluorophores composition in tissues due to the development of cancer. Native fluorescence spectroscopy analyzed by MCR-ALS may have the potential to be a new armamentarium.

UV Reflectance Spectroscopy Probes DNA and Protein Changes in Human Breast Tissues

OBJECTIVE The absorption spectrum obtained using diffuse reflectance measurements of malignant, fibroadenoma, and normal human breast tissues were studied. The spectral features in the spectrum were assigned to molecular components in the tissues. BACKGROUND DATA Over the past decade, the methods of fluorescence, excitation, and Raman spectroscopy have been studied as potential noninvasive diagnostic tools. Useful spectroscopic information may be obtained from absorption spectra of tissues as well. However, direct measurement of absorption spectra of tissues by conventional transmission means is complicated by multiple photon scattering in tissues. Diffuse reflectance spectrum offers an indirect way to obtain absorption spectrum. METHODS Excised malignant, fibroadenoma, and normal breast tissue samples without any treatment were obtained from pathology. Samples were placed in a quartz cuvette. The diffuse reflectance measurements between 250 nm to 650 nm were performed using an automated dual lamp spectrophotometer. The absorption spectra of breast tissues were obtained from the diffuse reflectance measurement. RESULTS Twenty-one invasive carcinoma, 20 mixed in situ and invasive carcinoma, 14 fibroadenoma, and 39 normal breast tissue samples were studied. The absorption spectra of breast tissues were obtained from diffuse reflectance spectra. Spectral features were assigned to DNA and proteins in human breast tissue. Amplitude of changes averaged over 275 nm to 285 nm and 255 nm to 265 nm and were found to be different for malignant, fibroadenoma, and normal breast tissues. These changes arise from differences in content of protein and DNA. CONCLUSION The peaks of absorption spectrum derived from diffuse reflectance measurements in the UV region revealed fingerprints from proteins and DNA components. The absorbance in the wavelength ranges of 275-285 nm and 255-265 nm were found to be different for malignant, fibroadenoma, and normal breast tissues. These differences provide a criterion to distinguish malignant from fibroadenoma and normal breast tissues.

Stokes shift spectroscopic analysis of multifluorophores for human cancer detection in breast and prostate tissues

Abstract. Stokes shift spectroscopy (S3) offers a novel and simpler way to rapidly recognize spectral fingerprints of multiple fluorophores in complex media such as in tissue. This spectroscopic technique can be used as an effective approach to detect cancer in tissue. The alterations of the measured S3 spectra between cancerous and normal tissues were observed in human breast and prostate samples. In order to obtain the optimal Stokes shift interval, Δλi, for the purpose of breast/prostate cancer detection using S3, the S3 spectra of a mixed aqueous solution of tryptophan, nicotinamide adenine dinucleotide, and flavin were measured with different Δλi values. The experimental results analyzed using nonnegative least square method show that there is a reduced contribution from collagen and an increased contribution from tryptophan to the S3 signal of the cancerous tissue as compared with those of the normal tissue. This study indicates that the changes of relative contents of tryptophan and collagen in tissue shown by the S3 spectra may present potential native biomarkers for breast and prostate cancer detection. S3 has the potential to be a new armamentarium.

Optical Spectroscopy of Benign and Malignant Breast Tissues

Fluorescence spectroscopy was applied to characterize normal, malignant and adipose breast tissues. Excitation, emission, and synchronized diffusive reflectance spectral scans were measured on over one hundred specimens for the purpose of developing an improved spectroscopic diagnostic technique. These techniques were able to successfully distinguish malignant tissue from adipose glandular fibrous and normal tissue. A sensitivity of 91% for fifty-six (56) malignant specimens with specificity of 91% for forty-six (46) benign tissue specimens has been achieved, using pathology as the golden standard.

Reorientation of the H2O cage studied by terahertz time-domain spectroscopy

The terahertz absorption spectrum of a thin film of liquid H2O of ∼14μm thickness showed a clear absorption mode at 1.56THz(∼53cm−1). This mode is attributed to the bending motion of the intermolecular hydrogen-bond coordinate in a water cage. The dielectric relaxation times of a slow τ1∼9ps and a fast τ2∼0.2ps component (0.4–2.0THz) were determined using a double Debye dielectric model.The terahertz absorption spectrum of a thin film of liquid H2O of ∼14μm thickness showed a clear absorption mode at 1.56THz(∼53cm−1). This mode is attributed to the bending motion of the intermolecular hydrogen-bond coordinate in a water cage. The dielectric relaxation times of a slow τ1∼9ps and a fast τ2∼0.2ps component (0.4–2.0THz) were determined using a double Debye dielectric model.

Biomarkers spectral subspace for cancer detection

Abstract. A novel approach to cancer detection in biomarkers spectral subspace (BSS) is proposed. The basis spectra of the subspace spanned by fluorescence spectra of biomarkers are obtained by the Gram-Schmidt method. A support vector machine classifier (SVM) is trained in the subspace. The spectrum of a sample tissue is projected onto and is classified in the subspace. In addition to sensitivity and specificity, the metrics of positive predictivity, Score1, maximum Score1, and accuracy (AC) are employed for performance evaluation. The proposed BSS using SVM is applied to breast cancer detection using four biomarkers: collagen, NADH, flavin, and elastin, with 340-nm excitation. It is found that the BSS SVM outperforms the approach based on multivariate curve resolution (MCR) using SVM and achieves the best performance of principal component analysis (PCA) using SVM among all combinations of PCs. The descent order of efficacy of the four biomarkers in the breast cancer detection of this experiment is collagen, NADH, elastin, and flavin. The advantage of BSS is twofold. First, all diagnostically useful information of biomarkers for cancer detection is retained while dimensionality of data is significantly reduced to obviate the curse of dimensionality. Second, the efficacy of biomarkers in cancer detection can be determined.

Direct observation of coherent rotational excitation, dephasing and depopulation of methanol and its isotopes using THz pulse radiation

Coherent transients are directly observed in the time-domain as a sequence of decreasing commensurate pulses in methanol (CH3OH) and its isotopes (CH3OD and CD3OD) gases to yield fundamental information on its dephasing and depopulation. The delay times between coherent pulses of ∼21, 22, and 26ps are measured for the CH3OH, CH3OD, and CD3OD corresponding to the inverse of rotational energy spacing for ΔJ=±1 transitions, respectively. The dephasing time T2=23±0.5ps and depopulation time T1=48±0.5ps were measured for CH3OH at room temperature.

Stokes shift emission spectroscopy of key biomolecules in human tissues

The Stokes-shifted emission spectra were measured for various photoactive biomolecules such as tryptophan, collagen, NADH and flavin in aqueous solution and tissue. Information is obtained on the molecular activity in the tissue. This new approach allows for the extraction of information not obtained from excitation and/or fluorescence spectroscopy for a single spectral scan.

Spectroscopic properties of tryptophan and bacteria

Fluorescence spectra of tryptophan and bacteria were measured at different concentrations using a Mediscience CD-Scan unit. The emission spectra of tryptophan were obtained using an excitation wavelength at 280 nm. The excitation spectra were obtained at the emission of 340 nm. The minimum detectable concentration of tryptophan was found to be 10-8 M. The emission spectra for bacteria were probed at 340 nm. The minimum detectable number of bacteria in a beam of the excitation light was determined to be about 30. Assuming that the emission band at 340 nm of bacteria comes from tryptophan, the number of tryptophan per bacterium was estimated to be 108. This approach to determine the number is almost consistent with that obtained using a weight method.