This Key Event Relationship is licensed under the Creative Commons BY-SA license. This license allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator. The license allows for commercial use. If you remix, adapt, or build upon the material, you must license the modified material under identical terms.

Relationship: 2809

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Energy Deposition leads to Modified Proteins

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Energy Deposition

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

Modified Proteins

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name	Adjacency	Weight of Evidence	Quantitative Understanding	Point of Contact	Author Status	OECD Status
Deposition of energy leading to occurrence of cataracts	adjacent	Moderate	Moderate	Vinita Chauhan (send email)	Open for citation & comment	WPHA/WNT Endorsed

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. More help

Term	Scientific Term	Evidence	Link
human	Homo sapiens	Moderate	NCBI
rat	Rattus norvegicus	High	NCBI
mouse	Mus musculus	Moderate	NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help

Sex	Evidence
Unspecific	High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

Term	Evidence
All life stages	High

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Energy deposition, such as that released from radiation (ionizing or non-ionizing) in sensitive lens cells can lead to protein modifications such as phosphorylation, disulfide bond formation, D-Asp formation, and carbonylation, among other changes (Hamada et al., 2014; Lipman et al., 1988; Reisz et al., 2014). It is important to note that ionizing and non-ionizing radiation work by different mechanisms; ionizing radiation has enough energy to remove tightly bound electrons from atoms, leading to the formation of ions (charged particles), while the absorption of non-ionizing radiation leads to molecular vibrations and rotations, resulting in heat generation (Alcócer et al., 2020). The modifications arise as energy deposited onto a cell interacts with molecules (e.g. proteins, lipids, DNA), altering the redox balance of the cell, and resulting in amino acid modifications (Neves-Petersen et al., 2012). These changes cause structural and functional molecular-level damage to the proteins, such as aggregation (Reisz et al., 2014; Hamada et al., 2014). However, the extent of damage from different types of protein modifications would vary as these protein changes may be short-lived due to the cell life cycle and the associated regulation of the protein (Basisty et al., 2018).

Under homeostatic conditions, cells inherently have a set amount of total protein that are soluble (Pace et al., 2004). These properties can be disrupted by the deposition of energy. The interaction of a soluble protein with large amounts of energy can change its molecular weight and solubility through deamidation and the formation of disulfide bonds (Hanson et al., 2000; Reddy 1990; Miesbauer et al., 1994).

Other types of protein modification can also occur, including protein carbonylation and D-Asp formation (Reisz et al., 2014; Hamada et al., 2014). Protein carbonylation, a result of reactive oxygen species (ROS), is the post-translational addition of carbonyl to the protein’s side chain, these can observably be increased when a cell is exposed to ionizing radiation (Resiz et al., 2014). Inversion of amino acids from the L to D conformation can also occur in response to the ionization events or thermal energy released from radiation, this contributes to protein quaternary structure changes (Fujii et al., 2004).

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings. Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

The strategy for collating the evidence to support the relationship is described in Kozbenko et al 2022. Briefly, a scoping review methodology was used to prioritize studies based on a population, exposure, outcome, endpoint statement.

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Overall Weight of Evidence: Moderate

Biological Plausibility

Addresses the biological rationale for a connection between KEupstream and KEdownstream. This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured. More help

The biological plausibility of the relationship between deposited energy leading to modified proteins is moderately supported by the literature. It is well accepted that deposition of energy, from ionizing sources (γ-rays, X-rays) and non-ionizing sources (ultraviolet (UV) radiation) can increase protein modifying events, resulting in structural changes to the protein (Hamada et al., 2014; Van Kuijk et al., 1991; Lipman et al., 1988; Reisz et al., 2014). These modifications include deamidation, oxidation, and disulfide bonds (Hanson et al., 2000; Kim et al., 2016; Kim et al., 2015; Lipman et al., 1988). Human, mouse, and rat models have been studied and prominent changes observed include increased cross-linking, altered water-solubility, and increased aggregation (Fochler & Durchschlag, 1997; Van Kuijk, 1991; Davies & Delsignore, 1987).

Deposition of energy can alter the protein profile within a cell leading to a decrease in water-soluble proteins and an increase in water-insoluble proteins. This arises from structural-level modifications to the protein amino acids. The amino acids that are particularly at risk are aromatic amino acids, as well as cysteine residues, which are known to have the lowest redox potential (Reisz et al., 2014). Aromatic amino acids can be converted into photosensitizers (Walrant & Santus, 1974). Tryptophan, which is present in alpha crystalline molecules, can also be converted into kynurenine when exposed to UV radiation, through the destabilization of its structural protein folds (Xia et al., 2013). Exposure to UV and photons, has been associated with the aggregation of water-soluble proteins and an increase in insoluble protein content (Van Kuijk, 1991; Wang et al., 2010; Hamada et al., 2014;). Stressors such as γ-rays can also lead to protein oxidation via reactive oxygen species (ROS), including protein cross-linking and hydrophobic protein interactions (Davies & Delsignore, 1987; Lee & Song, 2002). Additionally, at high concentrations, ROS from radiation can oxidize and cross-link proteins, producing insoluble protein clumps (Young, 1994).

Protein aggregation has also been shown to result from the formation of disulfide bonds. (Lipman et al., 1988). It is believed that when energy is deposited, it causes the protein molecule to unfold from its native structural conformation and aggregate through disulfide connections with other modified proteins (Chen et al., 2013). Treatment with a reducing agent that cleaves disulfide bonds results in the release of the aggregates, suggesting that the bonds between the sulfide sites have an impact on protein aggregation (Reddy, 1990).

Empirical Evidence

Provides specific (citable) evidence that supports the idea of a change in the upstream KE (KEupstream) leading to, or being associated with, a subsequent change in the downstream KE (KEdownstream), assuming the perturbation of KEupstream is sufficient. More help

The empirical evidence relating to this KER moderately supports the relationship between the deposition of energy and modified proteins. A variety of protein changes have been used to measure this relationship, including molecular weight, solubility, and the presence of oxidation sites. Most of the data comes from high (>2 Gy) dose studies, with in vivo and in vitro models for taxa such as rodents, bovines, and humans (Zigler & Goosey, 1981; Anbaraki et al., 2016; Andley et al., 1990; Zigman et al., 1975; Abdelkawi et al., 2008; Shang et al. 1994; Shin et al., 2004).

Dose Concordance

Strong evidence is available in lens cells to support a dose response relationship between energy deposition and protein modification. A study showed, that lens crystallin proteins continuously irradiated in vitro for 24 hrs using UV from white light-daylight fluorescent lamps with a measurement of 500 ft-c (foot candles) contained high molecular weight proteins relative to controls (Zigler & Goosey, 1981). In another study, cross-linking of lens crystallin proteins was observed in vitro as early as 30 minutes and within 2-4 hrs following UV exposure. There was also a gradual decrease in native protein concentration with increasing dose of UV (Anbaraki et al., 2016). Other studies also show similar findings, whereby there is a shift in the percentage of high molecular weight proteins following in vitro exposure of lens cells to 140 J/m2 UV, but not 70 J/m2 (Andley et al., 1990). Zigman et al showed alterations in lens protein water-insolubility after 8 weeks of continuous UV exposure on in vivo eyes, with no significant change after 4 weeks (Zigman et al., 1975). In radon exposed whole lenses, no significant change to soluble lens protein content were observed until 6 weeks of continuous in vivo radon treatments, whereby, levels reached 0.85x control, and then continued decreasing at 8 weeks of exposure (Abdelkawi et al., 2008). Other studies using ionizing radiation have shown protein modifications as a result of oxidative by-products from radiation exposure. For example, Trp 69, Met 70, and Met 102 in γ-crystallins was shown to be oxidized after exposure to 5 Gy of γ-rays. Kim et al. (2015) observed naked lens cortex protein modifications from 5% in the control to 9% after 10 Gy of γ -rays and at the maximum dose tested of 50 Gy (Shang et al., 1994).

Time Concordance

No evidence available.

Essentiality

Radiation exposure is essential to increase levels of modified proteins above control levels. Studies that do not deposit energy are observed to have no downstream effects. One study found that the sham-exposed group exhibited less cross-linking of lens crystallin proteins compared to in vitro 4 hr UV exposed groups (Anbaraki et al., 2016). Additionally, relatively lower doses of X-ray exposures result in lower levels of protein alterations compared to lens cells receiving a higher dose. Water insoluble lens proteins remain at low levels, compared to cells exposed to 8 weeks of UV, where the levels were observed to rise above 1.4x from controls (Zigman et al., 1975). Similarly, in lenses exposed to radon gas for 6 weeks, there was a 1.2x fold increase in the levels of lens proteins compared to unexposed cells (Abdelkawi et al., 2008).

Uncertainties and Inconsistencies

Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

Although the relationship is well- supported, the degree and type of modification can be variable depending on the exposure conditions. Significant increases in oxidized crystallin protein are seen anywhere from 5 Gy in vivo (Kim et al. 2015) to 50 Gy in vivo (Kim et al., 2016) to 270 Gy in vitro (Finley et al., 1998). This relationship is difficult to predict.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references. More help

Modulating Factor (MF)	MF Specification	Effect(s) on the KER	Reference(s)
Age	The absorption of radiation in the lens of the eye, such as UV, increases with age.	Free UV filters exist in the eye to help block UV from interacting with proteins in the lens. The filters, such as tryptophan metabolites, degrade as people age, reducing the protection for proteins in the lens.	Bron et al., 2000; Davies & Truscott, 2001; Truscott & Friedrich, 2016
Free Radical Scavengers	The addition of antioxidants attenuates the effect of energy deposition.	Sodium Azide (NaN₃) and Cystamine, free radical scavengers, reduce the amount of cross-linking of crystalline proteins.	Zigler & Goosey, 1981; Shin et al., 2004

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

The following tables provide representative examples of the relationship, unless otherwise indicated, all data is significantly significant.

Dose Concordance

Reference	Experiment Description	Result
Abdelkawi et al., 2008	In vivo, two-month-old adult male Swiss albino mice received whole-body radon exposure to 3.54 mJ m^-3 h for six continuous weeks (dose of 637.2 mJ m^-3) and the levels of soluble protein were measured using a Lowry assay.	Cells showed a decrease in soluble lens protein concentration (indicative of increased protein modification) to 0.85x control.
Abdelkwai, 2012	In vivo, male rats received whole-body exposure to 0.5 Gy/week of γ-rays and observed identified molecular weight changes in proteins using spectroscopy.	Cells showed an increase in crystallin molecular weight with each isoform, α, β-H, β-L, and γ increasing 28, 16, 27, and 54% relative to control.
Kim et al., 2015	In vitro, male rat lenses exposed to 2.8 Gy/h γ-ray and protein oxidation was detected using liquid chromatography-tandem mass spectroscopy.	A 5 Gy γ-ray treatment group had 10 sites of oxidation on water-soluble and water-insoluble γE- or γF-crystallin proteins.
Sherif & Abdelkawi, 2006	In vivo, male rat lenses received whole-body γ-ray exposure to 0.5 Gy/week and total soluble protein level was determined by the Lowry assay.	Rat lenses exposed to 0 - 4.0 Gy γ-rays showed a decrease in soluble lens protein (indicative of increased modified protein levels) with the maximum dose displaying a 1.6x decrease relative to control.
Shang et al., 1994	In vitro, bovine lens cortices exposed to 0-500 Gy at 3.96 Gy/min γ-rays and protein changes (β- and γ-crystallins) assessed using SDS-PAGE.	Cells exposed to 0-500 Gy displayed a linear increase in β-crystallin fragmentation above 10 Gy. They also displayed increased protein aggregates above 10 Gy, with the notable exception of β-crystallin which exhibited a slight drop below the trend line (but not below control) at 50 Gy.
Anbaraki et al., 2016	In vitro, bovine lens proteins exposed to 316 W/m²UV and protein modifications assessed using SDS-PAGE.	Increased cross-linking and oligomerization of UV-exposed lens proteins was observed Increase in dose caused an increase in higher molecular weight proteins, starting at 0.5 hr of light exposure, with another increase at 2 hrs of light. The non-native staining is relatively similar for 2-4hr exposures, but with increase dose, native staining decreases
Zigler & Goosey, 1981	In vitro, human lens proteins exposed to 12.5 W/m² UV and protein modification was detected using SDS-PAGE.	24 h exposure to UV resulted in increased molecular weight of crystallin proteins. This trend continued with the 48hr dose group.
Andley et al., 1990	In vitro, rabbit lens epithelial cells exposed to 70 or 140 Jm^-2 UVB and protein modifications assayed via SDS-PAGE and autoradiographic scans.	UVB irradiation caused a decrease in the amount of 37 kD protein that was produced and expelled from the cells. Exposure to 70 J/m² led to a 7% decrease in 37 kD protein levels and exposure to 140 J/m² led to a 50% decrease in 37 kD protein levels. However, most of the other proteins remained unchanged.
Moran et al., 2013	In vitro, human crystallins exposed to 35 W/m² UVB for 6 h and protein weight changes detected using SDS-PAGE.	Exposure to 35 Wm-2 UVB for 6 h results in increased concentration of γD-crystallin proteins above 20 kDa molecular weight compared to control.
Fochler & Durchschlag, 1997	In vitro, calf crystallins exposed to UV (60, 100, 150 kJ/m2) or X-rays (1, 5, 10 kGy). Changes in protein weight were detected using SDS-PAGE.	At all doses measured, there is either a shift or a disappearance of the alpha and gamma crystallins on the SDS-PAGE.
Zigman et al., 1975	In vivo, mice received whole-body exposure to 450 μW/cm² long-wave UV and insoluble protein level was assessed using SDS-PAGE.	At 4 weeks of UV (12 hr on/off cycle), the treatment group and the control group were shown to diverge with a linear increase in the treatment group. At 8 weeks of UV (12 hr on/off cycle), the treatment group reached an insoluble protein level of 0.35 mg/lens, 1.4x control level.
Giblin et al., 2002	In vivo, male guinea pigs received whole-body exposure to 0.5 mW/cm² UVA and protein solubility changes were measured using the BCA protein assay.	Lens nucleus cells exposed to 4-5 months of UV-A had 276 mg/g water-soluble protein level. This is 20% less than the 343 mg/g seen in control groups. The cortex did not have significant differences.
Simpanya et al., 2008	In vivo, male guinea pigs received whole-body exposure to 0.5 mW/cm² UVA and protein changes were assayed using dynamic light scattering.	After 5 months exposure to UV-A, proteins in the nucleus had a higher average diameter compared to control. At 2.1 mm across the optical axis, the UV group had an average of 1020 diameter (arbitrary units), 5.67x the control's 180 average.
Fochler & Durchschlag, 1997	In vitro, sex calf crystallins exposed to UV (60, 100, 150 kJ/m2) or X-rays (1, 5, 10 kGy). Changes in protein weight were detected using SDS-PAGE.	At all doses measured, there is either a shift or a disappearance of the alpha and gamma crystallins on the SDS-PAGE.

Time Concordance

No evidence found.

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Time-scale

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Known Feedforward/Feedback loops influencing this KER

Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

N/A

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

This KER is plausible in all life stages, sexes, and organisms. The majority of the evidence is from in vivo male adult rats, and in vitro bovine models that do not specify sex.

References

List of the literature that was cited for this KER description. More help

Abdelkawi, S. (2012), “Lens crystallin response to whole body irradiation with single and fractionated doses of gamma radiation”, International Journal of Radiation Biology, Vol.88/8, Informa UK Ltd, London, https://doi.org/10.3109/09553002.2012.695097.

Abdelkawi, S., M. Abo-Elmagd and H. Soliman. (2008), “Development of cataract and corneal opacity in mice due to radon exposure”, Radiation Effects and Defects in Solids, Vol.163/7, Taylor & Francis, Oxfordshire, https://doi.org/10.1080/10420150701249603.

Anbaraki, A. et al. (2016), “Preventive role of lens antioxidant defense mechanism against riboflavin-mediated sunlight damaging of lens crystallin”, International Journal of Biological Macromolecules, Vol.91, Elsevier, Amsterdam, https://doi.org/10.1016/j.ijbiomac.2016.06.047.

Andley, U. et al. (1990), “Effect of ultraviolet-b radiation on protein synthesis in cultured ens epithelial cells”, Current Eye Research, Vol.9/11, Taylor & Francis, Oxfordshire, https://doi.org/10.3109/02713689008997583.

Basisty, Nathan et al. (2018) “Protein Turnover in Aging and Longevity”, Proteomics, Vol.18, https://doi.org/10.1002/pmic.201700108

Bloemendal, H. et al. (2004), “Ageing and vision: structure, stability and function of lens crystallins”, Progress in Biophysics and Molecular Biology, Vol.86/3, Elsevier, Amsterdam, https://doi.org/10.1016/J.PBIOMOLBIO.2003.11.012.

Chen, Y. et al. (2013), “Ocular aldehyde dehydrogenases: Protection against ultraviolet damage and maintenance of transparency for vision”, Progress in Retinal and Eye Research, Vol.33/1, Elsevier, Amsterdam, https://doi.org/10.1016/j.preteyeres.2012.10.001.

Davies, K.J.A. and M.E. Delsignore. (1987), “Protein damage and degradation by oxygen radicals. 3. Modification of secondary and tertiary structure”, Journal of Biological Chemistry, Vol.262/20, American Society for Biochemistry and Molecular Biology, Rockville, https://doi.org/10.1016/s0021-9258(18)48020-9.

Davies, M. and R. Truscott. (2001), “Photo-oxidation of proteins and its role in cataractogenesis”, Journal of Photochemistry and Photobiology B: Biology, Vol.63/1-3, Elsevier, Amsterdam, https://doi.org/10.1016/s1011-1344(01)00208-1.

Finley, E. et al. (1998), “Radiolysis-induced oxidation of bovine alpha-crystallin", Photochemistry and Photobiology, Vol.68/1, Wiley-Blackwell. Hoboken, https://doi.org/10.1111/j.1751-1097.1998.tb03245.x.

Fochler, C. and H. Durchschlag. (1997), “Investigation of irradiated eye-lens proteins by analytical ultracentrifugation and other techniques”, Progress in Colloid and Polymer Science, Vol.107, Springer, Berlin, https://doi.org/10.1007/BFb0118020.

Fujii, N., H. Uchida, and T. Saito (2004), “The damaging effect of UV-C irradiation on lens alpha-crystallin”, Molecular Vision, Vol. 10, United States, pp. 814-820

Geiger, T. and S. Clarke. (1987), “Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides: succinimide-linked reactions that contribute to protein degradation”, Journal of Biological Chemistry, Vol.262, American Society for Biochemistry and Molecular Biology, Rockville, https://doi.org/10.1016/s0021-9258(19)75855-4.

Giblin, F. et al. (2002), “UVA light in vivo reaches the nucleus of the guinea pig lens and produces deleterious, oxidative effects”, Experimental Eye Research, Vol.75/4, Academic Press Inc, Cambridge, https://doi.org/10.1006/exer.2002.2039.

Hamada, N. et al. (2014), “Emerging issues in radiogenic cataracts and cardiovascular disease”, Journal of Radiation Research, Vol.55/5, Oxford University Press, Oxford, https://doi.org/10.1093/jrr/rru036. 

Hanson, S. et al. (2000), “The major in vivo modifications of the human water-insoluble lens crystallins are disulfide bonds, deamidation, methionine oxidation and backbone cleavage”, Experimental Eye Research, Vol.71/2, Academic Press Inc, Cambridge, https://doi.org/10.1006/EXER.2000.0868.

Kim, I. et al. (2016), “One-shot LC–MS/MS analysis of post-translational modifications including oxidation and deamidation of rat lens α- and β-crystallins induced by γ-irradiation”, Amino Acids, Vol.48/12, Springer, Berlin, https://doi.org/10.1007/s00726-016-2324-y.

Kim, I. et al. (2015), “Site specific oxidation of amino acid residues in rat lens γ-crystallin induced by low-dose γ-irradiation”, Biochemical and Biophysical Research Communications, Vol.466/4, Elsevier, Amsterdam, https://doi.org/10.1016/j.bbrc.2015.09.075.

Kozbenko, T. et al. (2022), “Deploying elements of scoping review methods for adverse outcome pathway development: a space travel case example”, International Journal of Radiation Biology, 1–12. https://doi.org/10.1080/09553002.2022.2110306

Kuan, Y. et al. (2013), “Radiation processing of food proteins – A review on the recent developments”, Trends in Food Science & Technology, Vol.30/2, pp.105–120.

Lee, Y. and K.B. Song. (2002), “Effect of gamma-irradiation on the molecular properties of myoglobin”, Journal of Biochemistry and Molecular Biology, Vol.35/6, Biochemical Society of the Republic of Korea, Seoul, https://doi.org/10.5483/bmbrep.2002.35.6.590.

Lipman, R., B. Tripathi and R. Tripathi. (1988), “Cataracts induced by microwave and ionizing radiation”, Survey of Ophthalmology, Vol.33/3, Elsevier, Amsterdam, https://doi.org/10.1016/0039-6257(88)90088-4.

Miesbauer, L. R. et al. (1994), “Post-translational modifications of the water soluble human lens crystallins from young adults”, Journal of Biological Chemistry, Vol.269, American Society for Biochemistry and Molecular Biology, Rockville, https://doi.org/10.1016/s0021-9258(18)99902-3.

Moran, S. et al. (2013), “Amyloid fiber formation in human γd-crystallin induced by UV-B photodamage”, Biochemistry, Vol.52/36, American Chemical Society Publications, Washington, https://doi.org/10.1021/bi4008353.

Pace, C.N. et al. (2004), “Protein structure, stability and solubility in water and other solvents”, Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, Vol.359, Royal Society, London, https://doi.org/10.1098/RSTB.2004.1500.

Reddy, V.N. (1990), “Glutathione and its function in the lens—An overview”, Experimental Eye Research, Vol.50/6, Academic Press Inc, Cambridge, https://doi.org/10.1016/0014-4835(90)90127-G.

Reisz, J. et al. (2014), “Effects of ionizing radiation on biological molecules - mechanisms of damage and emerging methods of detection”, Antioxidants and Redox Signaling, Vol.21(2), Mary Ann Liebert Inc, Larchmont, https://doi.org/10.1089/ars.2013.5489.

Shang, F., L. Huang and A. Taylor. (1994), “Degradation of native and oxidized beta-and gamma-crystallin using bovine Lens epithelial cell and rabbit reticulocyte extracts”, Current Eye Research, Vol.13/6, Taylor & Francis, Oxfordshire, https://doi.org/10.3109/02713689408999870.

Sherif, S. and S. Abdelkawi. (2006). “Effect of fractionated dose of whole body gamma irradiation on eye lens proteins of rats”, Isotope and Radiation Research, Vol.38/3, Middle Eastern Regional Radioisotope Center for Arab Countries, Cario, pp.547-558.

Shin, D., et al. (2004), “Cell type-specific activation of intracellular transglutaminase 2 by oxidative stress or ultraviolet irradiation: Implications of transglutaminase 2 in age-related cataractogenesis”, Journal of Biological Chemistry, Vol.279/15, The American Society for Biochemistry and Molecular Biology, Rockville, https://doi.org/10.1074/jbc.M308734200.

Simpanya, F,M. et al. (2008), “Measurement of lens protein aggregation in vivo using dynamic light scattering in a guinea Pig/UVA model for nuclear cataract”, Photochemistry and Photobiology, Vol.84/6, Wiley-Blackwell, Hoboken, https://doi.org/10.1111/j.1751-1097.2008.00390.x.

Truscott, R. and M. Friedrich. (2016), “The etiology of human age-related cataract. Proteins don't last forever”, Biochimica et Biophysica Acta, Vol.1890/1, Elsevier, Amsterdam, https://doi.org/10.1016/j.bbagen.2015.08.016.

Van Kuijk, F. (1991), “Effects of ultraviolet light on the eye: Role of protective glasses”, Environmental Health Perspectives, Vol.96/30, National Institute of Environmental Health Sciences, Durham, https://doi.org/10.1289/ehp.9196177.

Walrant, P. and R. Santus. (1974), “Ultraviolet and N-Formyl-Kynurenine-Sensitized Photoinactivation of Bovine Carbonic Anhydrase: An Internal Photodynamic Effect”, Photochemistry and Photobiology, Vol.20/5, Wiley-Blackwell, Hoboken, https://doi.org/10.1111/j.1751-1097.1974.tb06600.x.

Wang, W., S. Nema and D. Teagarden (2010), “Protein aggregation- Pathways and influencing factors”, International Journal of Pharmaceutics, Vol.390/2, Elsevier, Amsterdam, https://doi.org/10.1016/j.ijpharm.2010.02.025.

Xia, Z. et al. (2013), “UV-radiation Induced Disruption of Dry-Cavities in Human γD-crystallin Results in Decreased Stability and Faster Unfolding”, Sci Rep Vol.3, https://doi.org/10.1038/srep01560.

Young, R. (1994), “The family of sunlight-related eye diseases”, Optometry and Vision Science, Vol.71/2, Lippincott Williams & Wilkins, Philadelphia, https://doi.org/10.1097/00006324-199402000-00013.

Zigler, S.J. and J. Goosey. (1981), “Photosensitized Oxidation in the Ocular Lens: Evidence for Photosensitizers Endogenous To the Human Lens”, Photochemistry and Photobiology, Vol.33/6, Wiley-Blackwell, Hoboken, https://doi.org/10.1111/j.1751-1097.1981.tb05505.x.

Zigman, S. et al. (1975), “The response of mouse ocular tissues to continuous near-UV light exposure”, Investigative Ophthalmology, Vol.14/September, Association for Research in Vision and Ophthalmology, Rockville, pp.710-713.