chemistry

Pladienolide B

Pladienolide B 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 Pladienolide B rather than just read about it. In short: Pladienolide B is a polyketide natural product that is made by the bacterium Streptomyces platensis MER-11107, which is a gram-positive bacteria isolated from soil in Japan. Pladienolide B is a molecule of interest due to potential anti-cancer properties.

Key takeaways

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

Reference excerpt

Pladienolide B is a polyketide natural product that is made by the bacterium Streptomyces platensis MER-11107, which is a gram-positive bacteria isolated from soil in Japan. Pladienolide B is a molecule of interest due to potential anti-cancer properties. The proposed mechanism of action of this molecule is via binding to and inhibiting the SF3B complex within the human spliceosome.

Biosynthesis As a polyketide, pladienolide B is synthesized in the polyketide synthase (PKS) type I pathway, a biosynthetic pathway that is derived from the fatty acid synthase (FAS) pathway. Polyketides are formed through the condensation of acyl-thioester units. The synthesis of pladienolide B begins with acyl transferase loading propionyl CoA onto the holo (activated) acyl carrier protein (ACP). The molecule is then extended ten times, each time by two carbon units, by iterative PKS (Figure 1). Figure 1 indicates the loading unit (malonyl CoA or methylmalonyl CoA) and tailoring enzymes for each module (turquoise enzyme clusters in part c of Figure 1). After the ten elongation modules, the active site serine residue of thioesterase (TE) acts as a nucleophile by attacking the ketone directly bound to CoA-SH. This nucleophilic attack causes CoA-SH to leave and thus transfers the elongated chain to TE. Then the hydroxyl group on carbon 11 acts as a nucleophile by attacking the terminal ketone so that carbons 1-11 form a cyclic, 12-membered ring, releasing TE in the process. This concludes the PKS portion of the biosynthesis, and thus results in the pladienolide B backbone structure. Post-PKS modifications: Acetyl-transferase (AT) transfers an acetyl group to carbon 7. The following step is either that a P450 I enzyme (PldB C6-hydroxylase) adds a hydroxyl group on carbon 6, and/or that an epoxide group is added between carbons 18 and 19 by P450 II (PldD C18-C19-epoxidase). Based on the purification results of these post-PKS compounds by Boothe et al., it seems that either hydroxylation or acetylation could occur first, but Boothe et al. found a that hydroxylation seems to occur first more than twice as often as acetylation occurs first. However, regardless of hydroxylation or acetylation occurring first, the result of these tailoring steps yields pladienolide B (Figure 1).

Carbons are numbered using the traditional IUPAC naming system in which C1 is the ketone carbon in the ring, and C23 is the terminal carbon on the chain.

References

Illustrations

Worked examples

Example 1 — a first encounter with Pladienolide B

Start with the simplest possible case. Write down what Pladienolide B 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 Pladienolide B 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 Pladienolide B 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 Pladienolide B

In research: Pladienolide B 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 Pladienolide B 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: Pladienolide B is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acetate esters, Epoxides, Heterocyclic compounds with 1 ring, so understanding it makes those chapters shorter.
In everyday life: Look for Pladienolide B 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 Pladienolide B in 20 minutes

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

Frequently asked questions

What is Pladienolide B in simple terms?

Why does Pladienolide B 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 Pladienolide B?

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 Pladienolide B.