biology

Reactive nitrogen species

Reactive nitrogen species is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Reactive nitrogen species rather than just read about it. In short: Reactive nitrogen species (RNS) are a family of antimicrobial molecules derived from nitric oxide (•NO) and superoxide (O2•−) produced via the enzymatic activity of inducible nitric oxide synthase 2 (NOS2) and NADPH oxidase respectively. NOS2 is expressed primarily in macrophages after induction by cytokines and microbial products, notably interferon-gamma (IFN-γ) and lipopolysaccharide (LPS).

Key takeaways

Reactive nitrogen species belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Reactive nitrogen species to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Reactive nitrogen species from memory before moving on to harder problems.

Reference excerpt

Reactive nitrogen species (RNS) are a family of antimicrobial molecules derived from nitric oxide (•NO) and superoxide (O2•−) produced via the enzymatic activity of inducible nitric oxide synthase 2 (NOS2) and NADPH oxidase respectively. NOS2 is expressed primarily in macrophages after induction by cytokines and microbial products, notably interferon-gamma (IFN-γ) and lipopolysaccharide (LPS). Reactive nitrogen species act together with reactive oxygen species (ROS) to damage cells, causing nitrosative stress. Therefore, these two species are often collectively referred to as ROS/RNS. Reactive nitrogen species are also continuously produced in plants as by-products of aerobic metabolism or in response to stress.

Types RNS are produced in animals starting with the reaction of nitric oxide (•NO) with superoxide (O2•−) to form peroxynitrite (ONOO−):

•NO (nitric oxide) + O2•− (superoxide) → ONOO− (peroxynitrite) Superoxide anion (O2−) is a reactive oxygen species that reacts quickly with nitric oxide (NO) in the vasculature. The reaction produces peroxynitrite and depletes the bioactivity of NO. This is important because NO is a key mediator in many important vascular functions including regulation of smooth muscle tone and blood pressure, platelet activation, and vascular cell signaling. Peroxynitrite itself is a highly reactive species which can directly react with various biological targets and components of the cell including lipids, thiols, amino acid residues, DNA bases, and low-molecular weight antioxidants. However, these reactions happen at a relatively slow rate. This slow reaction rate allows it to react more selectively throughout the cell. Peroxynitrite is able to get across cell membranes to some extent through anion channels. Additionally peroxynitrite can react with other molecules to form additional types of RNS including nitrogen dioxide (•NO2) and dinitrogen trioxide (N2O3) as well as other types of chemically reactive free radicals. Important reactions involving RNS include:

ONOO− + H+ → ONOOH (peroxynitrous acid) → •NO2 (nitrogen dioxide) + •OH (hydroxyl radical) ONOO− + CO2 (carbon dioxide) → ONOOCO2− (nitrosoperoxycarbonate) ONOOCO2− → •NO2 (nitrogen dioxide) + O=C(O•)O− (carbonate radical) •NO + •NO2 ⇌ N2O3 (dinitrogen trioxide)

Biological targets Peroxynitrite can react directly with proteins that contain transition metal centers. Therefore, it can modify proteins such as hemoglobin, myoglobin, and cytochrome c by oxidizing ferrous heme into its corresponding ferric forms. Peroxynitrite may also be able to change protein structure through the reaction with various amino acids in the peptide chain. The most common reaction with amino acids is cysteine oxidation. Another reaction is tyrosine nitration; however peroxynitrite does not react directly with tyrosine. Tyrosine reacts with other RNS that are produced by peroxynitrite. All of these reactions affect protein structure and function and thus have the potential to cause changes in the catalytic activity of enzymes, altered cytoskeletal organization, and impaired cell signal transduction.

See also Reactive oxygen species Reactive sulfur species Reactive carbonyl species

References

External links Short article on RN chemistry Archived 2009-11-25 at the Wayback Machine Article on global RN trends

Illustrations

Worked examples

Example 1 — a first encounter with Reactive nitrogen species

Start with the simplest possible case. Write down what Reactive nitrogen species claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Reactive nitrogen species before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Reactive nitrogen species ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Reactive nitrogen species

In research: Reactive nitrogen species appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Reactive nitrogen species in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Reactive nitrogen species is common in secondary-school and first-year university syllabi. It links to neighbouring topics Free radicals, Nitrogen compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Reactive nitrogen species outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Reactive nitrogen species in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Reactive nitrogen species means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Reactive nitrogen species out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Reactive nitrogen species in simple terms?

Why does Reactive nitrogen species matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Reactive nitrogen species?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Reactive nitrogen species.