Part of the answer can be found in a standard book of chemistry for undergraduates. Have a look at  the chapter related to pH and acido basic equilibria.

Some ROS have two forms, an acidic and a basic one.  both are linked by the acido-basic equilibrium and their pKa. i.e. for superoxide:

HO2 • = O2•- + H+ pKa=4.8 (approximate value)

Roughly, It means that if the pH is lower tthan the pKa, the acidic (protonated)  form is the most abundant and if the pH is higher than this value, the unprotonated form is dominant. Similar equilibrium exists for peroxynitrite, which has an acidic form HONOO, and for many other RNS.

The reactivity of protonated forms can differ from that of unprotonated ones. For instance HO2 • is a stronger oxidant than  O2•- and it can initiate lipid peroxidation. Peroxynitrous acid is more unstable than peroxynitrite and undergoes very fast decomposition leading to e.g. NO2• and •OH.

 there should not be a confusion between electron (redox reactions) and proton (acido basic reactions) transfer. Again have a look a a simple book of chemistry, chapter oxidation. As for antioxidants, their action is electron transfer (exactly reduction) and not proton transfer. similarly, the formation of H2O2 from HO2 is a redox reaction and it requires an electron donor (a reductant) while the proton is usually coming from the bulk.

 HO2 • + e- + H+ = H2O2

It can be superoxide (the disproportionation of O2-)

HO2 • + O2•- + H+ = H2O2 + O2

finally as for the local pH, it is  more difficult to answer. If the place is in contact with the bulk, then no it won't alter the proton availability becasue there are lots of buffers whose job is to provide protons (carbonate, phosphate…). Inside a protein it may be different.

At least in a phagosome, protons are consumed to convert superoxide to hydrogen peroxide. You will find few studies that talk about this. 

Fisher, A. B. (2009). Redox signaling across cell membranes. Antioxid Redox Signal 11, 1349–1356.

Winterbourn, C. C., and Kettle, A. J. (2013). Redox reactions and microbial killing in the neutrophil phagosome. Antioxid Redox Signal 18, 642–660.

Gaurav.

It would, and vice versa. It is really interesting regulatory mechanism. There are quite a lot of interesting info regarding this although it is still quite mysterious. 

http://www.nature.com/cdd/journal/v11/n9/full/4401466a.html

http://www.ncbi.nlm.nih.gov/pubmed/10501200?dopt=Abstract&holding=npg

http://www.ncbi.nlm.nih.gov/pubmed/11727924?dopt=Abstract&holding=npg

I will say yes, at least some of them. For peroxynitite it will be unstable in low pH. In low pH the chloride anion, H2O2, and nitrite can for OCl- in the presence of myeloperoxidase but it will be less so in neutral pH.    

It is known that protonation of superoxide anion (pK 4.9) stongly increases the reactivity. Damaging effects of superoxide could be more pronounced at low pH.

Part of the answer can be found in a standard book of chemistry for undergraduates. Have a look at  the chapter related to pH and acido basic equilibria.

Some ROS have two forms, an acidic and a basic one.  both are linked by the acido-basic equilibrium and their pKa. i.e. for superoxide:

HO2 • = O2•- + H+ pKa=4.8 (approximate value)

Roughly, It means that if the pH is lower tthan the pKa, the acidic (protonated)  form is the most abundant and if the pH is higher than this value, the unprotonated form is dominant. Similar equilibrium exists for peroxynitrite, which has an acidic form HONOO, and for many other RNS.

The reactivity of protonated forms can differ from that of unprotonated ones. For instance HO2 • is a stronger oxidant than  O2•- and it can initiate lipid peroxidation. Peroxynitrous acid is more unstable than peroxynitrite and undergoes very fast decomposition leading to e.g. NO2• and •OH.

 there should not be a confusion between electron (redox reactions) and proton (acido basic reactions) transfer. Again have a look a a simple book of chemistry, chapter oxidation. As for antioxidants, their action is electron transfer (exactly reduction) and not proton transfer. similarly, the formation of H2O2 from HO2 is a redox reaction and it requires an electron donor (a reductant) while the proton is usually coming from the bulk.

 HO2 • + e- + H+ = H2O2

It can be superoxide (the disproportionation of O2-)

HO2 • + O2•- + H+ = H2O2 + O2

finally as for the local pH, it is  more difficult to answer. If the place is in contact with the bulk, then no it won't alter the proton availability becasue there are lots of buffers whose job is to provide protons (carbonate, phosphate…). Inside a protein it may be different.

You have already had some good answers. I would only add that the mechanism of protection by anti-oxidants is not by protonation. Compounds like vitamin C and E react sacrificially with the reactive oxygen species. The reactions of reactive oxygen species are electron reactions. If a proton is also involved it is quite incidental, and is taken up from the medium. However, protonation can affect the concentration of the reacting species, and therefore the rate.

I learned a lot from the book by Halliwell and Gutteridge

People, the situation is much more complicated. There are two things: 1.  a person asks a question. Just because he is curious, but uneducated in the field. 2. The problem of oxidative stress is very complex because the matter is not only in the formation of oxygen radicals, but also in the metabolic features of organism. 

Therefore, the answer should be not too complicated but show the complexity of the problem. I have attached the chapter from my book, which is rather simple and popular to show the problem of oxygen radicals and oxidative stress. Many things still remain beyond the description in the chapter. I hope it will help to answer some questions. Protons are important, but onlt small part of the big problem.

I am going to echo Dr. West. The reactions of ROS/RNS in biological systems are mediated by electrons, and proton concentration will affect the availability of the reactants. The book by Halliwell and Gutteridge is indeed a good source, and it will help to give a more in-depth understanding of the issues involved with these reactions. The reactions which occur in biological systems will be determined by a number of factors including the reactivity of the ROS/RNS, as well as the reactivity and availability of the reactant (usually protein, DNA, or lipid). I have attached our review article which discusses the role of pH in the oxidative modification of protein thiols.

Article Oxidative Modification of Proteins: An Emerging Mechanism of...

This is a good question and many good answers. Certainly, superoxide concentration depends on pH, however superoxide participates in nucleophilic reactions and in the formation of hydrogen peroxide and peroxynitrite, therefore the effects of pH will be very complicated.

Chantal Houée-Levin has explained very well. In vivo, proton concentration alters the reactions of ROS/RNS.

I would like to add another 5 cents to the current discussion.

When discussing pH, we should remember several important issues: 1) pH is in most bulk environments, we usually consider cytosol and mitochondrial matrix, is highly buffered. In the matrix pH may remain constant even though the ΔΨ may drop significantly; 2) the mitochondrial matrix is a hard gel, therefore, if there are changes in pH they occur locally in a narrow space either near an enzyme, which produces or consumes a proton, or near the membrane; 3) The metabolic events, including production of superoxide radicals or their removal, which are coupled to other metabolic events, occur in the multienzyme complexes and proceed usually irreversibly.

One of the most important species of ROS is the hydroperoxyl radical, also known as the perhydroxyl radical, which is the protonated form of superoxide with the chemical formula HO2. Hydroperoxyl is formed through the transfer of a proton to an oxygen atom. The concentration of O2 in the lipid phase of the membrane is 4-5 times higher than in the extra-membrane environment, and the superoxide anion is rapidly extruded from the membranes. The superoxide anion, O2•−, and the hydroperoxyl radical are in equilibrium in aqueous solution: O2•− + H2O is in equilibrium with HO2 + OH−. The protonation/deprotonation equilibrium exhibits a pKa of 4.88; consequently, about 0.3% of any superoxide present in the cytosol of a typical cell is in the protonated form. Although HO2 is also less hydrophobic and thus excluded from the lipid phase of membranes, nevertheless, it is more soluble in lipids than superoxide anion. I think that major formation of HO2 occurs not in the cytosol, but in the water-containing space near the superoxide-producing center inside the membrane. Unlike O2−, which predominantly acts as a reductant, HO2 can act as an oxidant in a number of biologically important reactions, such as the abstraction of hydrogen atoms from tocopherol and polyunsaturated fatty acids in the lipid bilayer. As such, it may be an important initiator of lipid peroxidation. The concentration of HO2 in the membrane may depend on local pH. I think that changes of pH in the bulk environments (cytosol or incubation medium) have little influence on reactions, which occur locally in the membranes and the membrane’s micro-environment near the enzyme’s center where superoxide is formed.