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 lens
 Prevent 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 age
 Zero turnover
 Primarily terrestrial diet
 Globally 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 source
 All carbon in our bodies is derived from the food we eat
 Diet 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’s
 WWII
Other problems…
“It was our experience that the lens could be removed up
to three days post-mortem. After this period, postmortem 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 discovered
 Practicality for forensic use?
Other Methods of Age
Determination
 Teeth
 Dentine
 Aspartic acid racemization
 Radiocarbon dating
 Skeleton
 Partial 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.