Abdullah Almohammedi - Mechanism of Heme Protein Reactions in Heart Cells Monitored by Resonance Raman Spectroscopy

Over the past century, doctors and scientists faced many problems in limiting the spread of diseases, because it was so difficult to study the structure and changes of biological systems. However, over the past two decades, modern technologies have brought about many advances for medical and biological chemists. One of these is optical methods which help to mitigate this problem. In this article, Abdullah Almohammedi describes his research exploring what happens to the heart under conditions of cardiac stress.

About My Research

Single Cardiac Myocyte
Single Cardiac Myocyte
Optical methods are techniques based on laser or light technology. Spectroscopy is a general term for methods that investigate interactions between laser or light and matter. In fact, all methods of spectroscopy depend on the absorption and scattering of radiation; for example Resonance Raman spectroscopy (RRS), fluorescence spectroscopy and absorption spectroscopy.

Resonance Raman spectroscopy (RRS) is an optical method where the inelastic scattering of light is used to investigate the composition and structure of materials. It was discovered by Chandrasekhara Venkata Raman in 1928. In RRS, the frequency of incident light is equal to the frequency of a molecular absorption band. It has been used as a powerful tool to understand the structure and states of heme proteins. The vibrational bands of heme are well known. However, it has not  been used before to provide physiologically relevant information in terms of the concentration and state of heme proteins in heart cells.

There are exciting data showing that free heme may play a role in cardiac stress responses. So, the main focus of my project is:

  • to ask whether cardiac responses to stress include mechanisms involving heme
  • to understand whether cardiac responses to stress, such as ischema, involve changes in cellular heme composition
  • and to understand if heme plays a role in signalling stress responses in cardiac myocytes and whether this has the overall effect of increasing the tolerance of cardiac muscle to stress

To answer these questions we use the knowledge of physics, chemistry, and biology to develop new method to measure the concentration of heme and understand its local environment in control and ischaemic cardiac muscle cells.

Research Approach

The purpose of monitoring heme in heart cells is to understand whether heme plays a role in signalling stress responses in cardiac myocytes, so we use the knowledge of physics, chemistry and biology to develop new method to measure the concentration of heme and understand its local environment in control and ischaemic cardiac muscle cells.

Our methodology is novel. We are using lasers to manipulate heart cells and probe their internal chemical environment. Although I am based in the Department of Physics and Astronomy, this cutting-edge technology is employed in the Department of Chemistry to answer questions in cell biology that are relevant to human health.

The chemical reactions of heme proteins in cardiac myocytes have been monitored by resonance Raman spectroscopy. In these experiments, a single cell is isolated in a perfusion chamber. A laser is focussed onto the cell, and Raman frequencies and intensities of heme proteins are measured continuously by time-lapse spectroscopy.

The present data was obtained in collaboration with the Department of Cell Physiology and Pharmacology. We have monitored the binding of oxygen molecules to heme proteins and electron transfer processes involving heme proteins in a single heart cell by recording the inelastic scattering of light from a laser beam. These measurements have been made whilst a physiological response is stimulated in the heart cell.

Research Findings

New data has been obtained on the mechanisms of chemical processes that take place in heart cells under conditions of cardiac stress. These chemical processes involve a number of proteins that contain heme as a prosthetic group (i.e. myglobins, haemoglobins, cytochromes).

Cardiac myocytes are muscle cells responsible for controlling the heart rate. This is the first time that a Raman spectrum for a cardiac myocyte has been recorded using a laser wavelength which is resonant with the Soret band of heme. The Raman spectrum is dominated by the spectral signatures from heme at this excitation wavelength. We have determined the local concentrations of heme-containing proteins in cardiac myocytes. The exact frequencies and intensities of Raman peaks has provided information on the oxidation and spin state of iron, and the presence or absence of small molecules bound to heme. We have observed the time scales for chemical changes to take place in the heart cells by simulating conditions for cardiac stress. This has been done by reduction of oxygen levels, or introduction of other small molecules into the fluid surrounding the heart cell. In these examples, the heme proteins undergo a series of chemical reactions, and the individual steps are revealed in the spectra. Cardiac myocytes do not undergo cell death during the experiments. The purpose of monitoring heme in heart cells is to understand whether heme plays a role in signalling stress responses in cardiac myocytes. Our approach offers an alternative to recently developed methods for studying the molecular mechanisms of proteins that contain heme as a prosthetic group (i.e. myglobins, haemoglobins, cytochromes) in Cardiac myocytes  and red blood cells.

About Abdullah Almohammedi

Abdullah Almohammedi is a research student working towards completion of his doctoral degree in the Department of Physics and Astronomy.

Abdullah is supervised by Dr Andrew Hudson.

Department of Physics and Astronomy
University of Leicester
University Road
Leicester
LE1 7RH

Abdullah will present his work at the Festival of Postgraduate Research 27 June 2013 - see Abdullah's Festival poster.

The Festival is open to all members of the University community and the public - book your place here.

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