chemistry

SYBR Green I

SYBR Green I is a chemistry 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 SYBR Green I rather than just read about it. In short: SYBR Green I (SG) is an asymmetrical cyanine dye used as a nucleic acid stain in molecular biology. The SYBR family of dyes is produced by Molecular Probes Inc., now owned by Thermo Fisher Scientific.

Key takeaways

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

Reference excerpt

SYBR Green I (SG) is an asymmetrical cyanine dye used as a nucleic acid stain in molecular biology. The SYBR family of dyes is produced by Molecular Probes Inc., now owned by Thermo Fisher Scientific. SYBR Green I binds to DNA. The resulting DNA-dye-complex best absorbs 497 nanometer blue light (λmax = 497 nm) and emits green light (λmax = 520 nm). The stain preferentially binds to double-stranded DNA, but will stain single-stranded (ss) DNA with lower performance. SYBR Green can also stain RNA with a lower performance than ssDNA.

Uses SYBR Green finds usage in several areas of biochemistry and molecular biology. It is used as a dye for the quantification of double stranded DNA in some methods of quantitative PCR. It is also used to visualise DNA in gel electrophoresis. Higher concentrations of SYBR Green can be used to stain agarose gels in order to visualise the DNA present. In addition to labelling pure nucleic acids, SYBR Green can also be used for labelling of DNA within cells for flow cytometry and fluorescence microscopy. In these cases RNase treatment may be required to reduce background from RNA in the cells. A comprehensive study of Thiazole-Orange-Based DNA Dyes was published, involving SYBR Safe, SYBR Green, PicoGreen, SYTO-16, SYTO-9 and a new derivative TOPhBu. There, the syntheses of these compounds were published and they were characterised spectroscopically to quantify their fluorescence enhancement upon binding to double-stranded DNA. The ability of the dyes to detect DNA at low concentrations was evaluated using two new metrics, absolute fluorescence enhancement (AFE) and relative fluorescence enhancement (RFE). They were tested in qPCR experiments showing some important differences in the sensitivity and qPCR efficiency, which facilitate the DNA marker selection for analytical purposes. The study concluded that Sybr Green exhibits the highest fluorescence enhancement (AFE) and provides the best characteristic for PCR methods. The second best among ther studied dyes was TOPhBu with an analytical performance similar to Sybr Green.

Safety SYBR Green I is marketed as a replacement for ethidium bromide, a potential human mutagen, as both safer to work with and free from the complex waste disposal issues of ethidium bromide. However any small molecule capable of binding DNA with high affinity is a possible carcinogen, including SYBR Green. In a study using the Ames test, which measures the ability of chemicals to cause mutations, when assayed at the same concentration SYBR Green I was on the order of 30 times less mutagenic than ethidium bromide.

Similar cyanine dyes PicoGreen (PG) SYBR Safe SYBR Gold Thiazole orange (TO) Oxazole yellow (YO) Safe-Green Chai Green

Illustrations

Worked examples

Example 1 — a first encounter with SYBR Green I

Start with the simplest possible case. Write down what SYBR Green I claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 SYBR Green I 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 SYBR Green I 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 SYBR Green I

In research: SYBR Green I appears in chemistry 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 SYBR Green I 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: SYBR Green I is common in secondary-school and first-year university syllabi. It links to neighbouring topics Benzothiazoles, Cyanine dyes, Dimethylamino compounds, so understanding it makes those chapters shorter.
In everyday life: Look for SYBR Green I 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 SYBR Green I in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SYBR Green I 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 SYBR Green I out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SYBR Green I in simple terms?

Why does SYBR Green I matter?

Because it connects several chemistry 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 SYBR Green I?

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 SYBR Green I.