Moleculine

Passenger information

The lexicon

24 terms, each short enough to read between two stations. Every one points to the stop where it is used.

A

Affinity

How tightly a molecule holds on to its receptor. Tight binding does not guarantee a strong effect.

Agonist

A molecule that binds a receptor and activates it. Full agonists give the maximum response, partial agonists less.

B

Beta-arrestin

A protein that docks on an activated, tagged receptor, blocks its G protein and helps pull it off the surface.

SWhy Receptors Go Quiet

Bioavailability

The fraction of a dose that reaches the bloodstream in active form. For swallowed peptides it is usually very low.

Blood-brain barrier

Tightly sealed blood vessel lining plus support cells and pumps that restrict what enters brain tissue.

C

cAMP

Cyclic AMP, a small second messenger made inside cells when certain G proteins switch on adenylyl cyclase.

Certificate of analysis

A report from a laboratory describing tests done on one batch. Only as trustworthy as the lab and the raw data behind it.

D

Desensitization

A weaker response to the same stimulus after continued exposure, caused by changes at or near the receptor.

SWhy Receptors Go Quiet

E

Efficacy

How large a response a molecule produces once it is bound to a receptor.

Enteroendocrine cell

A sensor cell in the gut lining that releases hormones into the blood in response to the gut contents.

F

Fmoc

A protective cap used on the amino end of each amino acid during solid-phase synthesis, removed with mild base each cycle.

G

G protein

An intracellular helper protein that a GPCR activates to pass its message on.

GPCR

G protein-coupled receptor. A membrane protein crossing seven times; about 800 exist in humans.

H

Half-life

The time it takes for the amount of a substance in the body to fall by half.

HPLC

High-performance liquid chromatography. Separates a mixture as it flows through a column so each component appears as a peak.

I

Incretin

A gut hormone, such as GLP-1 or GIP, that boosts insulin release after a meal.

L

N

Net peptide content

The share of a dry powder that is actually peptide, as opposed to water and counter-ions.

Neuropeptide

A peptide released by nerve cells that modulates activity over a wider area and longer time than a classic transmitter.

MMessengers That Linger

S

Second messenger

A small molecule made inside the cell after a receptor is activated, which spreads and amplifies the signal.

Stratum corneum

The outermost, dead-cell layer of skin that forms the main barrier against water loss and entry of molecules.

T

V

Volume transmission

Signaling in which a messenger diffuses away from its release site to reach receptors on many cells nearby.

MMessengers That Linger

W

Wound phases

Hemostasis, inflammation, proliferation and remodeling: the overlapping stages of healing.