Crystallins are proteins, which are:

• Soluble

• Hydrophilic

• Separated into 3 groups (of varying molecular weights and 3D structures):

  • ​α, β and γ- crystallins​

• Tightly packed arrangement, contributing to increased refractive index of the lens

 

 

• TRANSPARENCY​ - Due to short range, liquid-like order in high concentrations of crystallin proteins

• Highly stable and present for a long time

• Alterations in chemical environments and varying light absorption:

  • Cause irregularities to the crystallins structural and functional properties 

 

 

Alpha (α)-crystallins

• Molecular chaperones for beta and gamma proteins 

 

• Job is to prevent denaturation and aggregation formation of the crystallins

  • So, limits light scatter and reduction in transparency.

• They do this by helping them fold correctly during synthesis and refolding                                                      if ever denaturation occurred.

 

• As a result of aggregation, the crystallins become water insoluble due to a                                                     change in density

 

• As the lens ages, the beta and gamma crystallins aggregate at an increasing rate

  • This means they are more hydrophobic and leads to loss in lens transparency

 

 

• Aggregation changes can be due to the absorption of ultraviolet (UV) radiation

  • Causes a molecular structure change

    • This increases lens protein aggregation.

    • Due to chemical bonds which break as a result of the absorption and dissipation of energy from the photons in the UV radiation 

 

• Along with UV absorption, the lens can undergo changes as it matures with age, deamidation, acetylation, oxidation, glycation and proteolysis, all which contribute to the degradation of the crystallins