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 Proteins

Long lived proteins found in the lens of the eye

Maintains transparency of the lensPrevent protein aggregation

Elongation of compact fibres of crystalline proteins results in lens formation

14C Dating of Lens Crystalline Proteins

Large 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

Assumptions

Lens 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

Cataracts

Deamidation

Solubility

Vitamin 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

Solubility

Amount of insoluble protein increases almost linearly with age

In 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 C

Vitamin C and its degradation products induce protein modifications in vivo via non-enzymatic glycation

Vitamin C levels are particularly high in the lens

Degradation 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

tissues

Seafood 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 & Analysis

13 people of varying ages

All from Denmark

Small sample size, limited population

Cannot 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 old

Often months or years before a body is discoveredPracticality for forensic use?

Other Methods of Age Determination

TeethDentineAspartic 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.