Can eye lens proteins be used to determine birth

year?Radiocarbon Dating of the human eye lens crystallines reveal

proteins without carbon turnover throughout life

Jace James & Lauren Erland

Lens Crystalline ProteinsLong lived proteins found in the lens of the eyeMaintains transparency of the lens

Prevent protein aggregation

Elongation of compact fibres of crystalline proteins results in lens formation

14C Dating of Lens Crystalline ProteinsLarge accumulation of 14C in the atmosphere

after development and testing of nuclear bombs during and after World War II

Levels are much lower in marine environments

AssumptionsLens crystallines formed as a single event in

the year of birth and do not degrade with ageZero turnover

Primarily terrestrial dietGlobally everyone has approximately the same diet

Lens Crystallines formed as a single event and show zero turnover CataractsDeamidationSolubilityVitamin C

Cataracts Age-related, protein aggregation disease

Denaturation & insolubilization of lens proteins Factors promoting cataract formation

UV light & ionizing radiation Diabetes, hypertension and advanced age Heavy smoking

Change from a reducing to an oxidizing environment environment results in protein unfolding Addition of oxygen atoms due to hydroxide radicals

Majority of the proteins in the nuclei of advanced ARN cataract lenses undergoing are due to extensive modification and protein unfolding

Deamidation Modifications that disrupt the order of crystallines

Deamidation Truncation Methylation Oxidation Disulfide bond formation Glycation Racemization

Modification significantly decreases the amount of intact crystallines even in young adults

Deamidation is the most abundant modification

>60% Amide group removed Leads to protein instability

SolubilityAmount of insoluble protein increases almost

linearly with ageIn ARN cataract, insoluble even in 8 M urea

increases progressively~ 50% total nuclear protein.

It has been estimated that all people will suffer from cataract if they live long enough

Proteins do change!

Vitamin CVitamin C and its degradation products induce

protein modifications in vivo via non-enzymatic glycation

Vitamin C levels are particularly high in the lensDegradation products damage proteins via

formation of advanced glycation end products.

Primarily terrestrial diet“Consumption of fish would have a significant effect

on the 14C content of the lenses because the 14C content is smaller than that in the atmosphere”

Humans use organic carbon as their carbon sourceAll carbon in our bodies is derived from the food we eatDiet completely determines the 14C content in our

tissuesSeafood accounts for 14-16% animal protein

consumed globally>1 billion rely on fish as their primary source of

animal protein

Global Fish Consumption (WHO)

Data Collection & Analysis13 people of varying agesAll from DenmarkSmall sample size, limited populationCannot accurately predict age of those born

before nuclear testing caused atmospheric build up of 14C 1950’sWWII

Other problems…“It was our experience that the lens could be

removed up to three days post-mortem. After this period, post-mortem degradation and putrefaction made it impossible to extract the lens, as it became more and more fluid and not intact in its capsule”

Cannot be used on corpses more than 3 days oldOften months or years before a body is discovered

Practicality for forensic use?

Other Methods of Age DeterminationTeeth

DentineAspartic acid racemizationRadiocarbon dating

SkeletonPartial or whole Can optimize techniques based on suspected age

Ie child, adult

In both cases age can be determined from a whole or partial skeleton or a (partially) decomposed body

Can only use this method of age determination for people living in Denmark, born after WWII, who do not eat fish and seafood…

… And cannot be used it if the victim has been dead more than three days…

… or had a history of lens degrading diseases.