IC50

The half maximal inhibitory concentration (IC₅₀) is a measure of the effectiveness of a substance in inhibiting a specific biological or biochemical function.

This quantitative measure indicates how much of a particular drug or other substance (inhibitor) is needed to inhibit a given biological process (or component of a process, i.e. an enzyme, cell, cell receptor or microorganism) by half. It is commonly used as a measure of antagonist drug potency in pharmacological research. According to the FDA, IC₅₀ represents the concentration of a drug that is required for 50% inhibition in vitro. It is comparable to an EC₅₀ for agonist drugs. EC₅₀ also represents the plasma concentration required for obtaining 50% of a maximum effect in vivo.

Determining the IC₅₀ of a drug

Functional antagonist assay

The IC₅₀ of a drug can be determined by constructing a dose-response curve and examining the effect of different concentrations of antagonist on reversing agonist activity. IC₅₀ values can be calculated for a given antagonist by determining the concentration needed to inhibit half of the maximum biological response of the agonist.

Intercity (Deutsche Bahn)

Intercity is the second-highest train classification in Germany, after the ICE. Intercity services are loco-hauled express services, usually over long-distances. There are Intercity routes throughout Germany, and routes generally operate with a two-hour frequency, with multiple routes giving a more frequent service on core routes. Intercity services are operated by the DB Fernverkehr sector of Deutsche Bahn.

The Intercity name was introduced in Germany in 1971, replacing the old F-Zug category, and was the top category of train in Germany until the introduction of the ICEs in the early 1990s. With the proliferation of ICE services, the role of IC trains has diminished slightly, and they have taken on the character of many former InterRegio trains. Nonetheless, Intercity trains still offer a very high standard of speed and comfort – all services convey first class accommodation, and most include catering – usually a Bistro Cafe, but some services include a restaurant. A number of Intercity services serve destinations outside of Germany; most of these are under the EuroCity classification.