The absorption spectrum of a chromophore is only partly determined by its chemical structure. The environment also affects the observed spectrum, which mainly can

be described by three parameters:

protonation/deprotonation (pH, RedOx);

• solvent polarity (dielectric constant of the solvent); and

• orientation effects.

TLS Online TPP Program

#Id: 1620

#Unit 4. Cell Communication and Cell Signaling

TLR4 is unique in binding both MyD88 (when it is in the plasma membrane, signaling its endocytosis) and TRIF (when it is in endosomes, after internalization).

TLS Online TPP Program

#Id: 1621

#Unit 4. Cell Communication and Cell Signaling

COX2, whose synthesis is induced by PRR activation in monocytes, macrophages, neutrophils, and mast cells, is key to converting the lipid intermediate arachidonic acid to prostaglandins, potent proinflammatory mediators.

TLS Online TPP Program

#Id: 1622

#Unit 4. Cell Communication and Cell Signaling

IFN-α or -β activates IFNAR to recruit and activate specific JAKs (JAK1 and Tyk2), which then activate specific STATs induce expression of three genes, Protein kinase R (PKR), which inhibits viral (and cellular) protein synthesis by inhibiting the elongation factor eIF2α; 2’,5’-oligoadenlyate A synthetase, which activates the ribonuclease RNase L that degrades viral mRNA; and Mx proteins, which inhibit both the transcription of viral genes into mRNAs and the assembly of virus particles.

TLS Online TPP Program

#Id: 1623

#Unit 4. Cell Communication and Cell Signaling

Defensins (α and β) Disrupt membranes of bacteria, fungi, protozoan.

TLS Online TPP Program

#Id: 1624

#Unit 4. Cell Communication and Cell Signaling

Lactoferrin Binds and sequesters iron, limiting growth of bacteria and fungi.

TLS Online TPP Program

#Id: 1625

#Unit 4. Cell Communication and Cell Signaling

Surfactant proteins SP-A, SP-D Block bacterial surface components; promotes phagocytosis.