Chromophore Formation Research Articles

Photochemical changes in absorption and fluorescence of DDM-containing epoxies

Photochemical changes in the optical characteristics of solid polymers form the basis for many important technologies, but few examples are demonstrated in diamine-cured epoxy, one of the most important structural polymer systems. We have observed that diamine-cured epoxies containing the 4,4′-diaminodiphenyl methane (DDM) framework display changes in both absorption and fluorescence in response to UV light. The change from original “blue” to photo-activated “red” emission can be accomplished by illuminating samples of DDM-containing epoxy with photons of 254 nm or 370 nm wavelengths, followed by excitation of the newly-generated red-emitting fluorophore with 350–400 nm light. Studies of the monomer constituents and of many formulations of diamine-cured epoxy identify the DDM structure as the responsive moiety, both from the epoxy or diamine monomer. The fluorescence change is accompanied by the formation of orange and green chromophores; the orange chromophore is the fluorophore, with a broad 410 nm excitation and 607 nm emission. Our work shows the “blue-to-red” transition to be irreversible and independent of atmospheric oxygen; the fluorophore’s impermanence with time and its radical spectral signature identify it as a reactive intermediate rather than a photo-oxidation product. The central methylene radical of the benzoidal DDM structure is proposed as a red-emitting fluorophore/orange chromophore, with the green chromophore being a quinoidal methine resulting from the DDM radical.

Sonogashira-type cross-coupling reactions catalyzed by copper complexes of pincer N-heterocyclic carbenes

Copper complexes of N-heterocyclic carbenes (NHC) have recently received great attention in catalysis, however, the application scope has been limited to neutral complexes bearing monodentate ligands. Herein, we report the synthesis and full characterization of a cationic Cu-pincer bis(NHC) complex with bulky tert-butyl wingtips that serves as catalyst for the coupling of aryl iodides and phenylacetylene, alongside its analogs with small alkyl substituents. Unlike other copper catalysts that require an inert atmosphere to prevent alkyne homocoupling, a competing side reaction to Sonogashira reaction, the Cu-pincer bis(NHC) complexes provide good to excellent cross-coupling yields in air. Interestingly, the reaction under argon affords substantially reduced cross-coupling, indicative of the oxygen involvement and its facilitating effect in the mechanism. In our controlled studies, the air-assisted cross-coupling reaction came to a complete stop when using a radical trap, suggesting the presence of a radical in the mechanism. Examining the reaction of Cu-pincer bis(NHC) complexes with oxygen via UV–vis spectroscopy reveals a dark green chromophore formation at −40 °C with strong absorbance (ε > 400 M−1cm−1) at 460 nm and 500 nm, likely due to a high-valent copper-oxygen adduct.

Intrinsic blue-green fluorescence in amyloyd fibrils

Proteins and polypeptides containing a high proportion of β-sheets have been recently reported to exhibit, in their amyloid aggregated states, an intrinsic fluorescence in the blue-green range of wavelength where the aromatic residues do not emit. Lately, growing attention has been devoted to the identification of a specific, structure-related fluorophore for the detection of amyloid aggregates due to their implications in the physio-pathology of neurodegenerative diseases and other aggregation-related diseases. Indeed, the appearance of blue-green fluorescence could be used as an alternative method for the investigation and the detection of the aggregation state without using external probes. Several hypotheses have been suggested to explain the molecular bases of this rather unusual intrinsic emission. In particular, it has been related to an expansion of the electronic delocalization of π-electrons of peptide bonds through the backbone-to-backbone hydrogen bonds connecting the β-sheets. Alternatively, the formation of the intrinsic chromophore has been associated to chemical modifications of the aromatic residues or arising from dipolar coupling between excited states of aromatic amino acids densely packed in the fibril structures. More recently, it has been proposed that the blue-green amyloid fluorophore does not require neither the presence of aromatic residues nor multiple bond conjugation. In this study, we critically review the above hypotheses with particular attention to the electronic transitions responsible for the appearance of blue-green fluorescence in amyloid fibrils.

Equilibrating (L)FeIII-OOAc and (L)FeV(O) Species in Hydrocarbon Oxidations by Bio-Inspired Nonheme Iron Catalysts Using H2O2 and AcOH.

Inspired by the remarkable chemistry of the family of Rieske oxygenase enzymes, nonheme iron complexes of tetradentate N4 ligands have been developed to catalyze hydrocarbon oxidation reactions using H2O2 in the presence of added carboxylic acids. The observation that the stereo- and enantioselectivity of the oxidation products can be modulated by the electronic and steric properties of the acid implicates an oxidizing species that incorporates the carboxylate moiety. Frozen solutions of these catalytic mixtures generally exhibit EPR signals arising from two S = 1/2 intermediates, a highly anisotropic g2.7 subset (gmax = 2.58 to 2.78 and Δg = 0.85-1.2) that we assign to an FeIII-OOAc species and a less anisotropic g2.07 subset (g = 2.07, 2.01, and 1.96 and Δg ≈ 0.11) we associate with an FeV(O)(OAc) species. Kinetic studies on the reactions of iron complexes supported by the TPA (tris(pyridyl-2-methyl)amine) ligand family with H2O2/AcOH or AcOOH at -40 °C reveal the formation of a visible chromophore at 460 nm, which persists in a steady state phase and then decays exponentially upon depletion of the peroxo oxidant with a rate constant that is substrate independent. Remarkably, the duration of this steady state phase can be modulated by the nature of the substrate and its concentration, which is a rarely observed phenomenon. A numerical simulation of this behavior as a function of substrate type and concentration affords a kinetic model in which the two S = 1/2 intermediates exist in a dynamic equilibrium that is modulated by the electronic properties of the supporting ligands. This notion is supported by EPR studies of the reaction mixtures. Importantly, these studies unambiguously show that the g2.07 species, and not the g2.7 species, is responsible for substrate oxidation in the (L)FeII/H2O2/AcOH catalytic system. Instead the g2.7 species appears to be off-pathway and serves as a reservoir for the g2.07 species. These findings will be helpful not only for the design of regio- and stereospecific nonheme iron oxidation catalysts but also for providing insight into the mechanisms of the remarkably versatile oxidants formed by nature's most potent oxygenases.

Triplet Excited State of BODIPY Accessed by Charge Recombination and Its Application in Triplet-Triplet Annihilation Upconversion.

The triplet excited state properties of two BODIPY phenothiazine dyads (BDP-1 and BDP-2) with different lengths of linker and orientations of the components were studied. The triplet state formation of BODIPY chromophore was achieved via photoinduced electron transfer (PET) and charge recombination (CR). BDP-1 has a longer linker between the phenothiazine and the BODIPY chromophore than BDP-2. Moreover, the two chromophores in BDP-2 assume a more orthogonal geometry both at the ground and in the first excited state (87°) than that of BDP-1 (34-40°). The fluorescence of the BODIPY moiety was significantly quenched in the dyads. The charge separation (CS) and CR dynamics of the dyads were studied with femtosecond transient absorption spectroscopy (kCS = 2.2 × 1011 s-1 and 2 × 1012 s-1 for BDP-1 and BDP-2, respectively; kCR = 4.5 × 1010 and 1.5 × 1011 s-1 for BDP-1 and BDP-2, respectively; in acetonitrile). Formation of the triplet excited state of the BODIPY moiety was observed for both dyads upon photoexcitation, and the triplet state quantum yield depends on both the linker length and the orientation of the chromophores. Triplet state quantum yields are 13.4 and 97.5% and lifetimes are 13 and 116 μs for BDP-1 and BDP-2, respectively. The spin-orbit charge transfer (SO-CT) mechanism is proposed to be responsible for the efficient triplet state formation. The dyads were used for triplet-triplet annihilation (TTA) upconversion, showing an upconversion quantum yield up to 3.2%.

Chinese handmade mulberry paper: Generation of reactive oxygen species and sensitivity to photodegradation

Abstract Handmade mulberry paper is a traditional bark paper of China dating back nearly two millennia and is still a popular medium used today for preserving and restoring Asian paper artefacts. In the present study, samples of modern Chinese mulberry paper from different traditional manufacturers were artificially aged by exposure to UVA radiation. Their degradation patterns and associated generation of superoxide anions and hydrogen peroxides were determined by means of various spectroscopic techniques following our previous approach. Furthermore, electron spin resonance (ESR) spectroscopy using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin-trapping agent was employed to detect hydroxyl radicals in irradiated paper as well as to provide additional information for the photodegradation mechanism. Like Xuan paper, Chinese handmade mulberry paper exhibited blue fluorescence (λex = 340 − 400 nm; λem = 450 − 480 nm) consistent with it originating from a number of naturally-occurring hydroxylcoumarins. UVA irradiation of papers of different origins resulted in varying changes to the fluorescent species, which, together with the hydrolysis or formation of chromophores absorbing in the visible region, leads to the photobleaching or photoyellowing of paper. The extent of photodiscolouration of different papers correlate with their relative rates of the production of reactive oxygen species (ROS), including hydrogen peroxides, superoxide anions and hydroxyl radicals. SEM-EDS analyses revealed that the Chinese mulberry paper studied in the work had high levels of calcium and phosphorous, together with a much lesser amount of potassium, iron and copper, which probably originate from details in their manufacturing methods. Papers containing high concentrations of these metal ions also exhibited higher yields of ROS, which contribute to a higher level of oxidative stress and thereby affects their photostability. The main mechanism for the photodegradation of Chinese mulberry paper is proposed to be a sensitised oxidation via the formation of activated ROS, catalysed by the presence of transition metal ions, particularly ferric and cupric, and was accelerated by other factors such as moisture. This study has provided detailed knowledge for the photodegradation process of Chinese mulberry paper, which aims to assist the development of effective treatments for the restoration of important paper cultural heritage objects.

Smartphone Application for Methanol Determination in Sugar Cane Spirits Employing Digital Image-Based Method

A simple, accurate, and low-cost analytical procedure for methanol determination in sugarcane spirits (cachaca) employing analysis of digital images is presented. A portable system with cheap materials and lighting system to obtain images from a smartphone was built and an RGB system was used for analytical purposes. The reaction for determination of methanol in beverages consists in methanol oxidation to methanal, and consequent formation of a violet chromophore in the presence of chromotropic acid on heating in an oven at 80 °C for 15 min. From the system optimization, analytical curves that showed good linearity for the green channel (from RGB) was built, with regression coefficient (R 2) of 0.998. Relevant matrix effect in the samples was not verified, since the recovery percentage ranged from 83 to 110%. The results of methanol concentration in six cachaca samples obtained by the developed method were compared with using the spectrophotometric method with a confidence level of 95% (n = 3). The developed method has some economic and environmental benefits, since it has low reagent consumption with 800 μL per measured spot, as well as, it presents cheap and handle-easy devices, which encourages the quality control of this toxic and undesirable contaminant for smallholders and industries on production of sugar cane spirits.

PvdN Enzyme Catalyzes a Periplasmic Pyoverdine Modification

Pyoverdines are high affinity siderophores produced by a broad range of pseudomonads to enhance growth under iron deficiency. They are especially relevant for pathogenic and mutualistic strains that inhabit iron-limited environments. Pyoverdines are generated from non-ribosomally synthesized highly modified peptides. They all contain an aromatic chromophore that is formed in the periplasm by intramolecular cyclization steps. Although the cytoplasmic peptide synthesis and side-chain modifications are well characterized, the periplasmic maturation steps are far from understood. Out of five periplasmic enzymes, PvdM, PvdN, PvdO, PvdP, and PvdQ, functions have been attributed only to PvdP and PvdQ. The other three enzymes are also regarded as essential for siderophore biosynthesis. The structure of PvdN has been solved recently, but no function could be assigned. Here we present the first in-frame deletion of the PvdN-encoding gene. Unexpectedly, PvdN turned out to be required for a specific modification of pyoverdine, whereas the overall amount of fluorescent pyoverdines was not altered by the mutation. The mutant strain grew normally under iron-limiting conditions. Mass spectrometry identified the PvdN-dependent modification as a transformation of the N-terminal glutamic acid to a succinamide. We postulate a pathway for this transformation catalyzed by the enzyme PvdN, which is most likely functional in the case of all pyoverdines.

Effects of Ageing on the Color and Surface Chemistry of Paulownia Wood (P. elongata) from Fast Growing Crops

The behavior of paulownia wood (Paulownia elongata) was investigated using three different ageing tests: simulated natural ageing under the influence of light under indoor conditions, temperature-induced ageing in the dark, and UV-induced ageing. Ageing effects were evaluated by color measurements in the CIE Lab system. Simulated natural ageing of wood in indoor conditions (6 months) and UV-accelerated ageing (72 h) are complex and dynamic processes, which resulted mostly in yellowing of the samples due to photo-degradation. Temperature-induced ageing (288 h at 100 C) resulted mostly in a rapid and visible darkening of the paulownia wood. Comparative in-time evolution of color changes during accelerated UV ageing testing and simulated natural ageing testing under indoor conditions allowed the estimation of an acceleration index of about 50X. Fourier transform infrared spectroscopy (FTIR) was used to examine specific chemistry changes occurring during these ageing tests. UV light from natural or artificial sources caused primarily lignin degradation followed by oxidative processes leading to carbonyl-containing chromophores. Temperature-induced partial degradation of hemicelluloses and oxidative processes resulted in the formation of chromophores containing mostly conjugated carbonyl groups. This research highlighted that paulownia wood (P. elongata) is quite sensitive to ageing under the action of light and temperature, which cause notable color and surface chemistry changes.

Characterization of Chromophoric Water-Soluble Organic Matter in Urban, Forest, and Marine Aerosols by HR-ToF-AMS Analysis and Excitation-Emission Matrix Spectroscopy.

Chromophoric water-soluble organic matter in atmospheric aerosols potentially plays an important role in aqueous reactions and light absorption by organics. The fluorescence and chemical-structural characteristics of the chromophoric water-soluble organic matter in submicron aerosols collected in urban, forest, and marine environments (Nagoya, Kii Peninsula, and the tropical Eastern Pacific) were investigated using excitation-emission matrices (EEMs) and a high-resolution aerosol mass spectrometer. A total of three types of water-soluble chromophores, two with fluorescence characteristics similar to those of humiclike substances (HULIS-1 and HULIS-2) and one with fluorescence characteristics similar to those of protein compounds (PLOM), were identified in atmospheric aerosols by parallel factor analysis (PARAFAC) for EEMs. We found that the chromophore components of HULIS-1 and -2 were associated with highly and less-oxygenated structures, respectively, which may provide a clue to understanding the chemical formation or loss of organic chromophores in atmospheric aerosols. Whereas HULIS-1 was ubiquitous in water-soluble chromophores over different environments, HULIS-2 was abundant only in terrestrial aerosols, and PLOM was abundant in marine aerosols. These findings are useful for further studies regarding the classification and source identification of chromophores in atmospheric aerosols.

Non-excitable fluorescent protein orthologs found in ctenophores.

BackgroundFluorescent proteins are optically active proteins found across many clades in metazoans. A fluorescent protein was recently identified in a ctenophore, but this has been suggested to derive from a cnidarian, raising again the question of origins of this group of proteins.ResultsThrough analysis of transcriptome data from 30 ctenophores, we identified a member of an orthologous group of proteins similar to fluorescent proteins in each of them, as well as in the genome of Mnemiopsis leidyi. These orthologs lack canonical residues involved in chromophore formation, suggesting another function.ConclusionsThe phylogenetic position of the ctenophore protein family among fluorescent proteins suggests that this gene was present in the common ancestor of all ctenophores and that the fluorescent protein previously found in a ctenophore actually derives from a siphonophore.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0738-5) contains supplementary material, which is available to authorized users.

Preventive role of lens antioxidant defense mechanism against riboflavin-mediated sunlight damaging of lens crystallins

The main components of sunlight reaching the eye lens are UVA and visible light exerting their photo-damaging effects indirectly by the aid of endogenous photosensitizer molecules such as riboflavin (RF). In this study, lens proteins solutions were incubated with RF and exposed to the sunlight. Then, gel mobility shift analysis and different spectroscopic assessments were applied to examine the structural damaging effects of solar radiation on these proteins. Exposure of lens proteins to direct sunlight, in the presence of RF, leads to marked structural crosslinking, oligomerization and proteolytic instability. These structural damages were also accompanied with reduction in the emission fluorescence of Trp and Tyr and appearance of a new absorption peak between 300 and 400nm which can be related to formation of new chromophores. Also, photo-oxidation of lens crystallins increases their oligomeric size distribution as examined by dynamic light scattering analysis. The above mentioned structural insults, as potential sources of sunlight-induced senile cataract and blindness, were significantly attenuated in the presence of ascorbic acid and glutathione which are two important components of lens antioxidant defense system. Therefore, the powerful antioxidant defense mechanism of eye lens is an important barrier against molecular photo-damaging effects of solar radiations during the life span.

Detecting ethanol and acetaldehyde by simple and ultrasensitive fluorimetric methods in compound foods

There is a need for simple, accurate, and rapid analysis of ethanol (Eth) and acetaldehyde (AA) in a wide variety of beverages and foods. A novel enzymatic assay coupled to formation of fluorescent chromophore is presented. Eth detection was further improved by adding semicarbazide to the reaction mixture, which interacts with AA and prevents its inhibitory effect on Eth oxidation. The limits of detection of Eth (0.5mg/L) and AA (0.9mg/L) are comparable with the performance of modern gas chromatography techniques. The repeatability of Eth and AA detection in various foods (9% on average) was lower than that with commercial kits (23%). The high sensitivity of the developed method enables detection of AA in common foods [e.g., bio-yogurt (12.2mg/L), and the existence of endogenous Eth (1.8mg/L) and AA (2.0mg/L) in bacteria-free non-fermented bovine milk], which could not measured so far by enzymatic methods.

The influence of the exposure conditions on the chemical and physical changes of polyester–urethane coatings during photodegradation

The influence of the conditions of artificial degradation experiments on the photodegradation process of polyester–urethane clearcoats has been studied by comparing three types of exposure experiments with different conditions regarding the spectral power distribution (SPD), the exposure atmosphere (aerobic and anaerobic) and the presence of water. The presence of short wavelengths (λ < 295 nm) in the SPD largely influences the depth-inhomogeneity of degradation with respect to the optical properties and the chemical composition of the coating. The availability of oxygen in the exposure atmosphere determines the degradation pathway that is followed, such as to what extent the photo-oxidative breakage of urethane bonds or the formation of yellow chromophores due to aromatic crosslinking reactions occurs. Indentations at the surfaces of virgin and degraded coatings showed an increase in Young's modulus and hardness when degraded under aerobic conditions, while degradation under anaerobic conditions did not lead to significant changes. The presence of water is responsible for increasing the surface roughness of the coating during degradation, which directly influences the coating's gloss retention. Several time-independent correlations between the changes in chemical, optical and mechanical properties of coatings resulting from different exposure experiments have been established.

GFP Loss-of-Function Mutations in Arabidopsis thaliana.

Green fluorescent protein (GFP) and related fluorescent proteins are widely used in biological research to monitor gene expression and protein localization in living cells. The GFP chromophore is generated spontaneously in the presence of oxygen by a multi-step reaction involving cyclization of the internal tripeptide Ser65 (or Thr65)-Tyr66-Gly67, which is embedded in the center of an 11-stranded β-barrel structure. Random and site-specific mutagenesis has been used to optimize GFP fluorescence and create derivatives with novel properties. However, loss-of-function mutations that would aid in understanding GFP protein folding and chromophore formation have not been fully cataloged. Here we report a collection of ethyl methansulfonate–induced GFP loss-of-function mutations in the model plant Arabidopsis thaliana. Mutations that alter residues important for chromophore maturation, such as Arg96 and Ser205, greatly reduce or extinguish fluorescence without dramatically altering GFP protein accumulation. By contrast, other loss-of-fluorescence mutations substantially diminish the amount of GFP protein, suggesting that they compromise protein stability. Many mutations in this category generate substitutions of highly conserved glycine residues, including the following: Gly67 in the chromogenic tripeptide; Gly31, Gly33, and Gly35 in the second β-strand; and Gly20, Gly91, and Gly127 in the lids of the β-barrel scaffold. Our genetic analysis supports conclusions from structural and biochemical studies and demonstrates a critical role for multiple, highly conserved glycine residues in GFP protein stability.

Molecular selectivity of brown carbon chromophores.

Complementary methods of high-resolution mass spectrometry and microspectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene SOA (LSOA) and α-pinene SOA (PSOA). The LSOA compounds readily formed adducts with Na(+) under electrospray ionization conditions, with only a small fraction of compounds detected in the protonated form. In contrast, a significant fraction of PSOA compounds appeared in the protonated form because of their increased molecular rigidity. Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas was detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl-imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the α-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

Electron beam irradiation of maltodextrin and cinnamyl alcohol mixtures: Influence of glycerol on cross-linking

The influence of glycerol on the electron beam-induced changes in maltodextrins–cinnamyl alcohol (CA) blends is examined with respect to its influence on the degree of chain scission, grafting, and cross-linking. The study is relevant to radiation-induced polysaccharide modification, specifically in the perspective of using blended starch as a thermoplastic material, where glycerol is commonly used as a plasticizer. In the absence of CA, glycerol protects maltodextrin from chromophore formation onto the main chain, but also induces more chain scission. The presence of CA provides efficient radiation-protection against scission. Glycerol is shown to affect the interaction between maltodextrin and CA, most likely in the form of an inclusion complex when glycerol is absent. The global behavior under radiation is therefore governed by the physical interactions between the blend constituents rather than on the role of glycerol role as a plasticizer, or as an OH radical scavenger.

A highly responsive and selective fluorescent probe for imaging physiological hydrogen sulfide.

The discovery of hydrogen sulfide (H2S) as a novel gasotransmitter for cell signaling and other pathophysiological processes has spurred tremendous interest in developing analytical methods for its detection in biological systems. Herein, we report the development of a highly responsive and selective genetically encoded H2S probe, hsGFP, for the detection of H2S both in vitro and in living mammalian cells. hsGFP bestows a combination of favorable properties, including large fluorescence responses, high efficiency in folding and chromophore formation, and excellent sensitivity and selectivity toward H2S. As a genetically encoded probe, hsGFP can be readily and precisely localized to subcellular domains such as mitochondria, cell nuclei, and ion channels. hsGFP was further utilized to image H2S enzymatically produced from l-cysteine in human embryonic kidney (HEK) 293T cells.

Biosynthetic code for divergolide assembly in a bacterial mangrove endophyte.

Divergolides are structurally diverse ansamycins produced by a bacterial endophyte (Streptomyces sp.) of the mangrove tree Bruguiera gymnorrhiza. By genomic analyses a gene locus coding for the divergolide pathway was detected. The div gene cluster encodes genes for the biosynthesis of 3-amino-5-hydroxybenzoate and the rare extender units ethylmalonyl-CoA and isobutylmalonyl-CoA, polyketide assembly by a modular type I polyketide synthase (PKS), and enzymes involved in tailoring reactions, such as a Baeyer-Villiger oxygenase. A detailed PKS domain analysis confirmed the stereochemical integrity of the divergolides and provided valuable new insights into the formation of the diverse aromatic chromophores. The bioinformatic analyses and the isolation and full structural elucidation of four new divergolide congeners led to a revised biosynthetic model that illustrates the formation of four different types of ansamycin chromophores from a single polyketide precursor.

An ab-initio approach to cultural heritage: The case of ancient paper degradation

Paper is an important material for many applications. During the centuries, it has been the most widely used writing support and therefore paper degradation is a major issue for cultural heritage. The main component of paper is cellulose, one of the most abundant biomaterials on Earth. Cellulose oxidation is mainly responsible for the yellowing of the ancient samples, through the formation of chromophores. In order to investigate this issue and the chromophores’ role, we exploit the optical properties combining non-destructive experiments and theoretical calculations based on ab-initio techniques. In this paper, we illustrate the method and show its application to three ancient paper samples. The procedure we describe is a precious tool for cultural heritage preservation: indeed, the approach we present is based on non-invasive and non-destructive measurements that allows a microscopic understanding of cellulose-based artifacts degradation.