bme 486

Primary structure of proteins

Linear sequence of amino acids.

Secondary structure of proteins

Local folding into α-helices or β-sheets.

Tertiary structure of proteins

3D structure formed by side-chain interactions.

Quaternary structure of proteins

Assembly of multiple polypeptides.

Isoelectric point

The pH at which a protein has no net charge and is least soluble.

Collagen

Provides structural support in connective tissues.

Elastin

Provides elasticity to tissues.

Fibronectin

Facilitates cell adhesion.

Fibrinogen

Precursor to fibrin in blood clotting.

Albumin

Maintains osmotic pressure and transports substances.

Hemoglobin

Transports oxygen in blood.

Myoglobin

Stores oxygen in muscles.

Immunoglobulin G

Neutralizes pathogens.

Lysozyme

Breaks down bacterial cell walls.

Trypsin

Digestive enzyme that cleaves peptide bonds.

RGD

(Arg-Gly-Asp) is a cell adhesion motif in fibronectin that binds to integrins, facilitating cell attachment.

Interactions between proteins and biomaterial surfaces

Electrostatic, hydrogen bonding, van der Waals, hydrophobic, and covalent interactions.

Effect of protein size on biomaterial binding

Larger proteins have more contact sites but diffuse slower, influencing binding affinity and rate.

Factors affecting protein arrival rate at surfaces

Diffusion, thermal convection, flow, and coupled transport mechanisms.

Adsorption isotherm in dimensionless form

Describes surface coverage (θ) as a function of protein concentration (C).

Γm in Langmuir equation

Maximum adsorption capacity.

K in Langmuir equation

Affinity constant indicating binding strength.

Molecular spreading

Unfolding of proteins to maximize contact with surfaces.

Orientation change in protein adsorption

Repositioning of proteins without unfolding.

Desorption of proteins

The process by which proteins leave a surface.

Protein exchange

When one protein is replaced by another with higher affinity on a surface.

Vroman effect

Initial adsorption of abundant, smaller proteins followed by replacement by larger, higher-affinity proteins.

Deformation of erythrocytes

Enables red blood cells to pass through narrow capillaries without blocking blood flow.

Platelet plug formation stages

Adhesion, activation, and aggregation of platelets.

Intrinsic coagulation pathway

Initiated by contact with collagen or biomaterial.

Extrinsic coagulation pathway

Triggered by tissue factor release from damaged cells.

Function of thrombin

Converts fibrinogen to fibrin.

Function of tissue plasminogen activator (tPA)

Activates plasminogen to plasmin.

Function of plasmin

Degrades fibrin clots (fibrinolysis).

How heparin functions

Enhances antithrombin III activity to inactivate thrombin and other clotting factors.

Fibrinolysis

Breakdown of fibrin clots by plasmin activated from plasminogen.

Functions of eosinophils

Combat parasites and modulate allergic responses.

Functions of basophils

Release histamine and mediate allergic responses.

Monocytes vs macrophages

Monocytes are immature blood cells; macrophages are their mature form in tissues performing phagocytosis.

Foreign body giant cells

Fused macrophages that deal with large foreign objects.

Basophils vs mast cells

Basophils circulate in blood, while mast cells reside in tissues; both release histamine.

Macrophages vs neutrophils

Both perform phagocytosis; neutrophils are rapid responders and short-lived, while macrophages are long-lived and present antigens.

Opsonization

Marking particles with antibodies for phagocytosis.

Phagocytosis of digestible particles

Lysosomes degrade the particles.

Phagocytosis of indigestible particles

May cause chronic inflammation or fibrosis.

Four stages of phagocytic response

Chemotaxis, adherence, ingestion, and digestion.

Lamellipodia

Actin-based protrusions that facilitate cell migration.

Diapedesis

Movement of leukocytes through vessel walls.

Outcome of smooth biomaterial surfaces

Less protein adsorption and thrombosis.

Outcome of rough biomaterial surfaces

Enhanced protein adsorption and cell adhesion.