oxidative stress

Examples of oxidative stress in the following topics:

• Regulation of Sigma Factor Translation

  • The RpoS is critical in the general stress responses and can either function in promoting survival during environmental stresses, but can also prepare the cell for stresses.
  • Small noncoding RNAs are able to sense environmental changes and stresses resulting in increased expression of RpoS protein.
  • These small noncoding RNAs are capable of sensing changes in temperature (DsrA), cell surface stress (RprA) and oxidative stress (OxyS).

• The Pentose Phosphate Shunt

  • There are two distinct phases in the pathway: the oxidative phase and the non-oxidative phase .
  • The first is the oxidative phase in which glucose-6-phosphate is converted to ribulose-5-phosphate.
  • The second phase of this pathway is the non-oxidative synthesis of 5-carbon sugars.
  • Additionally, NADPH can be used by cells to prevent oxidative stress.
  • Outline the two major phases of the pentose phosphate shunt: oxidative and non-oxidative phases

• Bacterial Differentiation

  • However, this consistency could be affected in some circumstances (such as environmental stress) and changes in bacterial shape and size.
  • For instance, rod shapes may allow bacteria to attach more readily in environments with shear stress (e.g., in flowing water).
  • Oxidative stress, nutrient limitation, DNA damage and antibiotics exposure are some stress conditions to which bacteria respond, altering their DNA replication and cell division.
  • Filamentous bacteria have been considered to be over-stressed, sick and dying members of the population.
  • Nutritional stress can change bacterial morphology.

• Dissociation

  • Coping is expending conscious effort to solve personal and interpersonal problems, and seeking to minimize or tolerate stress or conflict.
  • Coping through dissociation is often associated with post-traumatic stress syndrome.
  • Substances with dissociative properties include ketamine, nitrous oxide, alcohol, LSD, tiletamine, marijuana, dextromethorphan, PCP, methoxetamine, salvia, and muscimol.
  • Dissociative disorders are sometimes triggered by trauma, but may be preceded only by stress, psychoactive substances, or no identifiable trigger at all.

• General Properties of Metals

  • Typically they are malleable and ductile, deforming under stress without cleaving.
  • An example is the reaction with oxygen in the air to form oxides over various timescales (iron rusts over years, while potassium burns in seconds).
  • The transition metals (such as iron, copper, zinc, and nickel) are slower to oxidize because they form a passivating layer of oxide that protects the interior.
  • Some metals form a barrier layer of oxide on their surface, which cannot be penetrated by further oxygen molecules.

• Oxidation Numbers of Metals in Coordination Compounds

  • Transition metals typically form several oxidation states and therefore have several oxidation numbers.
  • This oxidation number is an indicator of the degree of oxidation (loss of electrons) of an atom in a chemical compound.
  • O2- and S2- have oxidation numbers of -2.
  • In a molecule or compound, the oxidation number is the sum of the oxidation numbers of its constituent atoms.
  • The oxidation number of H is +1 (H+ has an oxidation number of +1).

• Oxides

  • Metal oxides typically contain an anion of oxygen in the oxidation state of −2.
  • Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or water.
  • Although most metal oxides are polymeric, some oxides are monomeric molecules.
  • Those attacked only by acids are basic oxides; those attacked only by bases are acidic oxides.
  • Metals tend to form basic oxides, non-metals tend to form acidic oxides, and amphoteric oxides are formed by elements near the boundary between metals and non-metals (metalloids).

• Properties of Quartz and Glass

  • Ordinary soda-lime glass appears colorless to the naked eye when it is thin, although iron (II) oxide (FeO) impurities of up to 0.1 % by weight produce a green tint.
  • Manganese dioxide can be added in small amounts to remove the green tint given by iron(II) oxide.
  • When used in art glass or studio glass, glass is colored using closely guarded recipes that involve specific combinations of metal oxides, melting temperatures, and 'cook' times.
  • Piezoelectricity is the ability to develop an electric potential upon the application of mechanical stress.
  • An early use of this property of quartz crystals was in phonograph pickups, where the mechanical movement of the stylus in the groove generates a proportional electrical voltage by creating stress within a crystal.

• Oxidations & Reductions

  • A parallel and independent method of characterizing organic reactions is by oxidation-reduction terminology.
  • Carbon atoms may have any oxidation state from –4 (e.g.
  • Fortunately, we need not determine the absolute oxidation state of each carbon atom in a molecule, but only the change in oxidation state of those carbons involved in a chemical transformation.
  • Carbon atoms colored blue are reduced, and those colored red are oxidized.
  • Peracid epoxidation and addition of bromine oxidize both carbon atoms, so these are termed oxidation reactions.

• Oxidation

  • The carbon atom of a carbonyl group has a relatively high oxidation state.
  • Useful tests for aldehydes, Tollens' test, Benedict's test & Fehling's test, take advantage of this ease of oxidation by using Ag(+) and Cu(2+) as oxidizing agents (oxidants).
  • The Fehling and Benedict tests use cupric cation as the oxidant.
  • This deep blue reagent is reduced to cuprous oxide, which precipitates as a red to yellow solid.
  • All these cation oxidations must be conducted under alkaline conditions.