meso-octamethylcalix[4]pyrrole: an old yet new transmembrane ion-pair transporter

Pore transport and ion-pair formation are critical mechanisms for the absorption and distribution of drugs in the body.
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited  but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...

Enzymes like flippase, floppase, and scramblase transfer phospholipids from one layer to another in the membrane, thereby affecting membrane asymmetry.
Flippase
Eukaryotic flippases are type-IV P-type ATPases or P4-ATPases belonging to P-type ATPase family proteins that are membrane-bound pumps involved in the ATP-mediated transport of ions and molecules across the membrane. Flippases flip specific phospholipids from the outer to the inner leaflet of a membrane. All P4-ATPases have one...

Transporters are essential membrane transport proteins with functions related to cell nutrition, homeostasis, communication, etc. Approximately 7% of all genes in the human genome code for transporters or transporter-related proteins.
Transporters are mainly composed of alpha-helices, built from bundles of ten or more helices traversing the plasma membrane. The solute-binding sites are located midway, where some of the helices are broken or distorted, making space for the binding site through...

The rough ER membrane synthesizes, assembles, and embeds transmembrane proteins in diverse topologies. These proteins function as transporters or channels and can remain in the ER membrane or are sent to the Golgi complex, lysosome, and cell membrane.
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...

In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or electrochemical gradient. There are two types of active transport: primary active transport and secondary active transport. Primary active transport utilizes chemical energy from ATP to drive protein pumps embedded in the cell membrane. With energy from ATP, the pumps transport ions against their electrochemical gradients—a direction they would not...

In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or electrochemical gradient. There are two types of active transport: primary active transport and secondary active transport. Primary active transport utilizes chemical energy from ATP to drive protein pumps that are embedded in the cell membrane. With energy from ATP, the pumps transport ions against their electrochemical gradients—a direction they...