H2S Helps Hearts

NO and H₂S are two important gases that regulate heart function in humans.

H₂S is a colourless, poisonous, flammable gas with the characteristic foul odour of rotten eggs at concentrations up to 100 parts per million. It is produced in swamps and sewers from the bacterial breakdown of organic matter in the absence of oxygen. It also occurs in volcanic gases, natural gas, and is produced naturally in the human body as a signalling molecule.

NO which also occurs naturally in the body, is highly reactive, having a biological lifetime of a few seconds, yet diffuses freely across membranes. People who live at high altitudes have higher levels of NO which helps them live with the lower oxygen concentration.

Scientists at the Peninsula Medical School at the University of Exeter and the National University of Singapore have analyzed the complex 'cross talk' between H₂S and NO and found that the interaction may offer potential strategies in the management of heart failure. The two gases were found to interact together to form a thiol-sensitive compound (probably HNO) which produces muscular contraction and muscular relaxation effects in the heart. This crosstalk suggests that there is the potential to produce a molecule that may be of benefit to the heart and which could be the basis of a new drug therapy based on elements that occur naturally in the body.

Reference
Qian-Chen Yong, Jia Ling Cheong, Fei Hua, Lih-Wen Deng, Yok Moi Khoo, How-Sung Lee, Alexis Perry, Mark Wood, Matthew Whiteman, Jin-Song Bian. Regulation of Heart Function by Endogenous Gaseous Mediators—Crosstalk Between Nitric Oxide and Hydrogen Sulfide. Antioxidants & Redox Signaling, 2011; 14 (11): 2081 DOI: 10.1089/ars.2010.3572

Further Reading
Naming Ionic Compounds
Molecular Mass (Formula Weight)
Percentage Composition
Concentration (ppm)
Lewis Structures
Shapes of Molecules
Molecule Polarity
Intermolecular Forces

Study Questions:

1. Name each of the following compounds:
   
   • H₂S
   • NO
   • HNO
2. Calculate the molecular mass (formula weight) for each of the following:
   
   • H₂S
   • NO
   • HNO
3. Calculate the percentage composition of each of the following:
   • H₂S
   • NO
   • HNO
4. H₂S can be detected by its odour at concentrations of 100ppm. Convert this to a concentration in
   
   • mg/L
   • μg/mL
   • % by mass (% by weight)
   • mol/L (M)
5. Draw a Lewis Structure (electron dot diagram) for each of the following molecules
   
   • H₂S
   • NO
   • HNO
6. Describe the shape of each of the following molecules:
   • H₂S
   • NO
   • HNO
7. Label each of the following molecules as polar or non-polar and explain why:
   • H₂S
   • NO
   • HNO
8. Which of the following molecules is most likely to have the highest boiling point, and explain why:
   • H₂S
   • NO
   • HNO