chemistry

Phloxine

Phloxine 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 Phloxine rather than just read about it. In short: Phloxine B (commonly known simply as phloxine) is a water-soluble red dye used for coloring drugs and cosmetics in the United States and coloring food in Japan. It is derived from fluorescein, but differs by the presence of four bromine atoms at positions 2, 4, 5 and 7 of the xanthene ring and four chlorine atoms in the carboxyphenyl ring.

Key takeaways

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

Reference excerpt

Phloxine B (commonly known simply as phloxine) is a water-soluble red dye used for coloring drugs and cosmetics in the United States and coloring food in Japan. It is derived from fluorescein, but differs by the presence of four bromine atoms at positions 2, 4, 5 and 7 of the xanthene ring and four chlorine atoms in the carboxyphenyl ring. It has an absorption maximum around 540 nm and an emission maximum around 564 nm. Apart from industrial use, phloxine B has functions as an antimicrobial substance, viability dye and biological stain. For example, it is used in hematoxylin-phloxine-saffron (HPS) staining to color the cytoplasm and connective tissue in shades of red.

Antimicrobial properties

Lethal dosage levels In the presence of light, phloxine B has a bactericidal effect on gram-positive strains, such as Bacillus subtilis, Bacillus cereus, and several methicillin-resistant Staphylococcus aureus (MRSA) strains. At a minimum inhibitory concentration of 25 μM, growth is reduced by 10-fold within 2.5 hours. At concentrations of 50 μM and 100 μM, growth is stopped completely and cell counts decrease by a factor of 104 to 105. For humans, the Food and Drug Administration deems phloxine B to be safe up to a daily dosage of 1.25 mg/kg.

Mechanism of action Bacteria exposed to phloxine B die from oxidative damage. Phloxine B ionizes in water to become a negatively charged ion that binds to positively charged cellular components . When phloxine B is subjected to light, debromination occurs and free radicals and singlet oxygen are formed. These compounds cause irreversible damage to the bacteria, leading to growth arrest and cell death. Gram-negative bacteria are phloxine B-resistant due to the outer cell membrane that surrounds them. This polysaccharide-coated lipid bilayer creates a permeability barrier that prevents efficient uptake of the compound. Addition of EDTA, which is known to strip the lipopolysaccharides and increase membrane permeability, removes the phloxine B resistance and allows gram-negative bacteria to be killed as well.

Measure of viability

Phloxine B can be used to stain dead cells of several yeasts, including Saccharomyces cerevisiae and Schizosaccharomyces pombe. When diluted in yeast growth media, the dye is unable to entere cell because of their membranes. Dead yeast cells lose membrane integrity, so phloxine B can enter and stain the intracellular cytosolic compounds. Therefore, staining is a measure of cell death. In cell counting assays, the number of fluorescent (i.e. dead) cells observed through a haemocytometer can be compared to the total number of cells to give a measure of mortality. The same principle can be applied at higher throughput by fluorescence-activated flow cytometry (FACS), where all phloxine B-stained cells in a sample are counted. [Note: some reports suggest that phloxine B is instead pumped out of live yeast cells but retained in dead/dying yeast cells. However, definitive evidence for either model is still needed.]

References

Illustrations

Worked examples

Example 1 — a first encounter with Phloxine

Start with the simplest possible case. Write down what Phloxine 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 Phloxine 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 Phloxine 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 Phloxine

In research: Phloxine 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 Phloxine 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: Phloxine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Benzofurans, Biaryls, Bromoarenes, so understanding it makes those chapters shorter.
In everyday life: Look for Phloxine 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Phloxine in 20 minutes

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

Frequently asked questions

What is Phloxine in simple terms?

Why does Phloxine 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 Phloxine?

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 Phloxine.