Analyst Blog

FTIR spectra of hormones triiodothyronine, thyroxine, diiodotyrosine, tyrosine and thyroid tissue

The combination of vibrational spectroscopy with mapping and imaging techniques to address important biochemical questions is an area of active and expanding research.  By subjecting adjacent tissue sections to standard histopathological screening and spectroscopic imaging, a greater understanding of the biochemical processes underlying tissue form and function can be achieved.

Researchers from Northeastern University, USA, and the Institute of Energy and Nuclear Research (IPEN), Sao Paolo, have used Fourier transform infrared (FTIR) microspectroscopy to examine healthy thyroid tissues. FTIR allows spatially resolved images, or maps, to be obtained by use of focal plane array detectors and spectral processing of the data then reveals chemical images.  In this HOT Analyst paper, Denise Zezell and coworkers present an example from their investigation of 80 different patient samples, which were analysed by transflection-mode FTIR mapping.  The approach was  applied to the study of healthy thyroid tissue and, with reference to thyroid specific hormones, iodination state. 

To know more about this research, click on the links below. This paper will be free to read for the next three weeks:

The characterization of normal thyroid tissue by micro-FTIR spectroscopy
Thiago M. Pereira, Denise M. Zezell, Benjamin Bird, Milos Miljković and Max Diem
Analyst, 2013,138, 7094-7100
DOI: 10.1039/C3AN00296A

Spectroscopic analysis of mycolic acid profiles

In bacterial-based diagnostics, the bacteria can evolve over time and it is important to be able to differentiate between multiple strains. Mycobacterium tuberculosis, which is responsible for causing tuberculosis (TB), has multiple drug-resistant strains. The most accurate method to identify toxic strains of TB, high performance liquid chromatography (HPLC), requires fluorescent labeling and extraction of the mycolic acids, from the outer membrane of the bacteria.

Researchers at the University of Georgia in the United States wanted a more direct detection method and approached this problem in two important aspects. They began by identifying the high molecular weight lipids within the bacteria using HPLC, gas chromatography (GC), and nuclear magnetic resonance (NMR) for several TB bacterial strains. NMR in particular was very important in identifying the structures of mycolic acids. Using the information from these techniques and surface enhanced Raman spectroscopy (SERS), they chemically classified the mycolic acid from both TB and non-TB strains. The SERS spectra underwent further statistical analysis and accurately identified different strains of TB label-free and with high sensitivity.

To know more about this research, click on the link below. This paper will be free to read for the next three weeks.

Identification of mycobacteria based on spectroscopic analyses of mycolic acid profiles
Omar E. Rivera-Betancourt, Russell Karls, Benjamin Grosse-Siestrup, Shelly Helms, Frederick Quinn and Richard A. Dluhy
Analyst, 2013,138, 6774-6785
DOI: 10.1039/C3AN01157G

LED-SERDS in Raman Spectroscopy

Raman spectroscopy finds a range of uses in analytical chemistry. Like infra-red (IR) spectroscopy it can provide a vibrational fingerprint by which compounds may be identified. Unlike IR, Raman is a scattering technique that does not require complex sample preparation, and water can be used as a solvent. In some samples, however, the Raman spectrum is rendered useless by intense fluorescence signals.

Chemical engineers Renata Adami (University of Salerno, Italy) and Johannes Kiefer (University of Aberdeen, UK) have developed a new approach to shifted-excitation Raman difference spectroscopy (SERDS) for suppression of fluorescence. SERDS experiments conventionally require expensive diode lasers, but in this Analyst paper Kiefer and Adami demonstrate the use of light-emitting diodes (LEDs) as an inexpensive light source. A dielectric bandpass filter narrows and stabilises the broad LED spectrum to make it usable for SERDS. While the resulting spectral resolution is low, different compounds and functional groups can be clearly distinguished using this method.

To read the full access, please click on the link below. This paper will be free to read for the next three weeks: