Question

Using the LIPID MAPS Database to Find Solubility Information Lipidomics has identified thousands of cellular lipids. LIPID MAPS is an online database containing over 40,000 unique lipid structures, as well as information on the chemical and physical properties of each lipid (www.lipidmaps.org). One important parameter when working with lipids is \(\log P\), where \(P\) is the octanol:water partition coefficient, an indicator of lipophilicity. a. Look up cholesterol, sphingosine, linoleic acid, and stearic acid in LIPID MAPS and use the reported \(\log P\) values to place them in order of increasing solubility in octanol. b. Pharmacologists often study \(\log P\) values when developing new drugs. Why would knowing a drug's \(\log\) \(P\) value be informative?

Short answer

Order lipids by increasing solubility in octanol using \\(\log P\\) values. \\(\log P\\) helps predict membrane absorption.

Step-by-step solution

Access the LIPID MAPS Database

Go to the LIPID MAPS website by entering www.lipidmaps.org into your web browser. This database contains detailed information about lipid structures and properties, including \(\log P\) values.

Search for Lipid Structures

Use the search feature on the LIPID MAPS website to find the specific lipids: cholesterol, sphingosine, linoleic acid, and stearic acid. Enter each lipid's name into the search bar.

Locate \\(\log P\\) Values

For each lipid, locate the section of its database entry that lists the chemical and physical properties. Record the \(\log P\) value for cholesterol, sphingosine, linoleic acid, and stearic acid.

Order by Increasing Solubility in Octanol

Based on the recorded \(\log P\) values, arrange the lipids in order of increasing solubility in octanol. Recall that a higher \(\log P\) indicates greater lipophilicity, hence lower solubility in water!

Interpret \\(\log P\\) Values for Pharmacology

Pharmacologists study \(\log P\) values because they indicate how well a drug can dissolve in lipids as opposed to water. Drugs with appropriate \(\log P\) values may more readily pass through cellular membranes, affecting their absorption and distribution within the body.

Key concepts

LIPID MAPS Database

The LIPID MAPS Database is a comprehensive online resource for lipidomics research. It contains information on over 40,000 unique lipid structures.
This database is especially useful for researchers, as it provides detailed chemical and physical properties for each lipid.
When you access LIPID MAPS, you'll find a user-friendly interface that allows you to search for specific lipids by name.

• All you need to do is type the lipid you are interested in into the search bar.
• Results will show comprehensive data about the lipid, including its \( ext{log} P\) value, chemical structure, and additional properties.

This makes LIPID MAPS an essential tool for those studying lipid solubility and related properties in the field of lipidomics.

Log P Values

The term "\( ext{log} P\) value" refers to the logarithm of the partition coefficient \(P\), which measures a compound's distribution between a water and a non-water (often organic) solvent, like octanol.
The \( ext{log} P\) value is crucial in understanding a substance's lipophilicity, which is its ability to dissolve in fats, oils, lipids, and non-polar solvents.

• A higher \( ext{log} P\) suggests that a substance is more lipophilic, indicating greater solubility in fatty substances than in water.
• Conversely, a lower \( ext{log} P\) means the substance is more water-soluble.

In pharmaceutical research, \( ext{log} P\) values help determine how likely a drug is to pass through cell membranes, thus aiding decisions in drug formulation and delivery.

Octanol:Water Partition Coefficient

The octanol:water partition coefficient, often represented as \(P\), is a measure of how a substance divides itself between an aqueous phase and an organic phase.
The organic phase is typically octanol.
This coefficient is important because it helps predict the absorption and distribution of substances, such as drugs, in biological systems.

• A high partition coefficient means the substance prefers the octanol phase, indicating it's likely to be absorbed into fatty tissues.
• A low partition coefficient means it favors the aqueous phase and is more soluble in water.

Pharmacologists and chemists analyze this coefficient to understand the behavior of substances within the body, which can directly affect efficacy and safety.

Lipid Structures

Lipid structures vary widely. Each type of lipid can serve distinct biological functions based on its chemical composition.
The variability in lipid structures arises from different ways their hydrocarbon chains and functional groups are arranged.

• Saturated lipids, like stearic acid, have no double bonds in their hydrocarbon chains, meaning they're typically solid at room temperature.
• Unsaturated lipids, such as linoleic acid, contain double bonds causing "kinks" in their structure and are usually liquid at room temperature.
• These structural differences play a role in determining the lipid's solubility and interaction with other molecules.

By studying lipid structures, researchers can better understand how they contribute to cellular processes and how modifications in structure could affect their function and solubility.