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1.
Am J Ophthalmol Case Rep ; 35: 102082, 2024 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-38841153

RESUMEN

Purpose: Although musculoskeletal involvement is the common presentation, studies have reported the incidence of sports related ocular trauma. Here we present the case reports of two patients who sustained injury in one of the fast growing sports - the pickleball, during play without eye protection. Observations: Two patients with history of injury during pickleball play presented to our clinic with varying spectrum of ocular presentations. First patient had an anterior segment involvement with hyphema and elevated intraocular pressure, and the second patient had both anterior and posterior segment involvement causing angle recession and commotio retinae. Conclusion: Ocular injuries related to various sports have been extensively described, our intent is to increase the awareness about the possible ocular injuries related to rising pickleball and that improved safety measures and appropriate education to the players could prevent such ocular injuries.

2.
Clin Ophthalmol ; 18: 1735-1742, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38912315

RESUMEN

Purpose: To evaluate the safety and effectiveness of the Ahmed ClearPath® (ACP) 250 mm2 glaucoma drainage device (GDD) in managing refractory primary open-angle glaucoma (POAG). Patients and Methods: This was a retrospective case series focused on adult patients diagnosed with severe POAG who underwent implantation of an ACP GDD. Over a 36-month follow-up period, data on intraocular pressure (IOP), the number of glaucoma medications, and complications were recorded. The primary objectives were to assess the reductions from baseline in both IOP and medication usage, through 36 months. Secondary objectives included the proportion of eyes achieving an IOP reduction of ≥ 20% from baseline at 36 months. Intraoperative and postoperative complications were also assessed. Results: Twelve eyes from 11 patients (mean age: 71.3 ± 14.1 years) met the inclusion criteria and were included in the study. All patients had severe POAG (n=11), with the majority being Caucasian (n=8) and female (n=10). The mean (standard deviation) IOP and number of glaucoma medications at baseline were 29 (7.6) mmHg and 3 (0.9), respectively. At 36 months, mean IOP was reduced to 10.6 (5.5) mmHg (-61.8%; p= 0.0008) and mean number of medications was reduced to 0.9 (0.9) (-71.4%; p=0.0005), with 88.9% of eyes achieving an IOP reduction by ≥20%. No vision threatening complications were observed. Conclusion: To our knowledge this is the first study to report 36-month outcomes of the novel ACP device in the treatment of refractory POAG. The safety profile and efficacy of the ACP was found to be comparable to that of other commonly utilized GDD models.

4.
Polymers (Basel) ; 16(8)2024 Apr 11.
Artículo en Inglés | MEDLINE | ID: mdl-38674972

RESUMEN

The development of sustainable materials from the valorization of waste is a good alternative to reducing the negative environmental impact of plastic packaging. The objectives of this study were to develop and characterize pectin-based composite films incorporated with cork or cork with either coffee grounds or walnut shells, as well as to test the films' genotoxicity, antioxidant properties, and biodegradation capacity in soil and seawater. The addition of cork, coffee grounds, or walnut shells modified the films' characteristics. The results showed that those films were thicker (0.487 ± 0.014 mm to 0.572 ± 0.014 mm), more opaque (around 100%), darker (L* = 25.30 ± 0.78 to 33.93 ± 0.84), and had a higher total phenolic content (3.17 ± 0.01 mg GA/g to 4.24 ± 0.02 mg GA/g). On the other hand, the films incorporated only with cork showed higher values of elongation at break (32.24 ± 1.88% to 36.30 ± 3.25%) but lower tensile strength (0.91 ± 0.19 MPa to 1.09 ± 0.08 MPa). All the films presented more heterogeneous and rougher microstructures than the pectin film. This study also revealed that the developed films do not contain DNA-reactive substances and that they are biodegradable in soil and seawater. These positive properties could subsequently make the developed films an interesting eco-friendly food packaging solution that contributes to the valorization of organic waste and by-products, thus promoting the circular economy and reducing the environmental impact of plastic materials.

5.
J Curr Glaucoma Pract ; 18(1): 10-15, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38585165

RESUMEN

Aim: To evaluate the success and safety of MicroPulse transscleral laser therapy (TLT) on intraocular pressure (IOP) reduction in adults with uncontrolled glaucoma using different total treatment durations, sweep velocities, and a number of sweeps utilizing the revised MicroPulse P3 delivery device. Materials and methods: A single-center Institutional Review Board (IRB) approved multiple cohort studies of MicroPulse TLT with the revised MicroPulse P3 delivery device, which was conducted in 61 eyes from 40 adults with uncontrolled glaucoma. Eyes that received 50-second (GI, GII, and GIII) and 60-second (GIV, GV, and GVI) treatment applications between May and October 2020 were reviewed. Each hemisphere received a total of five, four, or three sweeps. The patient's IOP and glaucoma medications were monitored over 12 months follow-up. Qualified success was defined as an IOP of ≤21 mm Hg and/or reduction of ≥20% from baseline at 12 months, with no secondary glaucoma reinterventions. Complete success was defined as meeting the above criteria with no increase in glaucoma medications at 12 months. All eyes requiring a glaucoma surgical intervention were considered a failure. Results: Qualified success was achieved in 83.6% of eyes, while complete success was achieved in 75.4% of eyes. In eyes receiving 50-second applications of five, four, or three sweeps (GI, GII, and GIII), 70, 90, and 91% achieved qualified success, respectively; in eyes receiving 60-second applications of five, four, or three sweeps (GIV, GV, and GVI), 78, 82, and 90% achieved qualified success, respectively. Within each subgroup, mean IOP reductions ranged from 32.8 to 49.4% and were statistically significant (p < 0.008). The failure rate was 16.4%, and at least one eye failed in each subgroup. Conclusions: MicroPulse TLT with the revised MicroPulse P3 delivery device and relatively low total energy levels is safe and effective at lowering IOP. Efficacy appears to increase with longer treatment durations and slower sweep velocities, but statistical differences between age and clinical differences between baseline IOP measurements limit comparison between subgroups. Clinical significance: There is a lack of literature evaluating the safety and IOP-lowering success of the revised MicroPulse P3 delivery device using different total treatment durations, sweep velocities, and number of sweeps. How to cite this article: Checo LA, Dorairaj S, Wagner IV, et al. Clinical Outcomes of MicroPulse Transscleral Laser Therapy with the Revised P3 Delivery Device. J Curr Glaucoma Pract 2024;18(1):10-15.

6.
Clin Ophthalmol ; 18: 713-721, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38468916

RESUMEN

Purpose: To report clinical outcomes of successful excisional goniotomy with the Kahook Dual Blade (KDB), through 60 months. Patients and methods: This was a noncomparative, single-surgeon, retrospective review of eyes receiving successful KDB goniotomy with or without concomitant phacoemulsification between October 2015 and January 2016 with five years of uninterrupted follow-up. Intraocular pressure (IOP), number of glaucoma medications, best corrected visual acuity (BCVA), and complications were recorded. Primary outcomes included changes from baseline in IOP, medication use, and BCVA, through five years. Results: Fifty-two eyes of 28 patients were analyzed. Most eyes had mild primary open angle glaucoma (73%). Of the eyes analyzed, 41 underwent combined surgery and 11 underwent standalone surgery. With all eyes combined, mean (standard deviation) baseline IOP was 21.0 (4.1) mmHg and mean baseline medication use was 1.8 (1.1) medications per eye. Across time points at months 6, 12, 24, 36, 48, and 60, mean postoperative IOP ranged from 13.0 to 13.7 mmHg, representing mean reductions of 7.3-8.0 mmHg (34.7-38.3%; p <0.0001 at every time point). Similarly, mean medication use ranged from 0.4 to 0.6 medications per eye, representing mean reductions of 1.2-1.4 medications (66-75.5%; p <0.0001 at every time point). Mean logMAR BCVA improved from 0.321 (0.177) preoperatively to 0.015 (0.035) at month 60 (p < 0.0001). Conclusion: In eyes not requiring secondary surgical procedures (eg, long-term surgical successes), excisional goniotomy provided clinically and statistically significant reductions in both IOP and the need for medications that were highly consistent through five years of follow-up. KDB goniotomy appears to be highly successful in Caucasian patients with open angle glaucoma on ≥1 IOP-lowering medications at baseline and with no history of prior ocular surgery. Successful excisional goniotomy with the KDB can be expected to improve long-term glaucoma-related visual outcomes through IOP reduction and to improve quality of life through medication reduction.

7.
Elife ; 122024 Jan 05.
Artículo en Inglés | MEDLINE | ID: mdl-38180785

RESUMEN

Acute stress can change our cognition and emotions, but what specific consequences this has for human prosocial behaviour is unclear. Previous studies have mainly investigated prosociality with financial transfers in economic games and produced conflicting results. Yet a core feature of many types of prosocial behaviour is that they are effortful. We therefore examined how acute stress changes our willingness to exert effort that benefits others. Healthy male participants - half of whom were put under acute stress - made decisions whether to exert physical effort to gain money for themselves or another person. With this design, we could independently assess the effects of acute stress on prosocial, compared to self-benefitting, effortful behaviour. Compared to controls (n = 45), participants in the stress group (n = 46) chose to exert effort more often for self- than for other-benefitting rewards at a low level of effort. Additionally, the adverse effects of stress on prosocial effort were particularly pronounced in more selfish participants. Neuroimaging combined with computational modelling revealed a putative neural mechanism underlying these effects: more stressed participants showed increased activation to subjective value in the dorsal anterior cingulate cortex and anterior insula when they themselves could benefit from their exerted effort relative to when someone else could. By using an effort-based task that better approximates real-life prosocial behaviour and incorporating trait differences in prosocial tendencies, our study provides important insights into how acute stress affects prosociality and its associated neural mechanisms.


Asunto(s)
Altruismo , Efectos Colaterales y Reacciones Adversas Relacionados con Medicamentos , Humanos , Masculino , Cognición , Simulación por Computador , Emociones
8.
Elife ; 122023 Nov 17.
Artículo en Inglés | MEDLINE | ID: mdl-37975654

RESUMEN

Influential accounts claim that violent video games (VVGs) decrease players' emotional empathy by desensitizing them to both virtual and real-life violence. However, scientific evidence for this claim is inconclusive and controversially debated. To assess the causal effect of VVGs on the behavioral and neural correlates of empathy and emotional reactivity to violence, we conducted a prospective experimental study using functional magnetic resonance imaging (fMRI). We recruited 89 male participants without prior VVG experience. Over the course of two weeks, participants played either a highly violent video game or a non-violent version of the same game. Before and after this period, participants completed an fMRI experiment with paradigms measuring their empathy for pain and emotional reactivity to violent images. Applying a Bayesian analysis approach throughout enabled us to find substantial evidence for the absence of an effect of VVGs on the behavioral and neural correlates of empathy. Moreover, participants in the VVG group were not desensitized to images of real-world violence. These results imply that short and controlled exposure to VVGs does not numb empathy nor the responses to real-world violence. We discuss the implications of our findings regarding the potential and limitations of experimental research on the causal effects of VVGs. While VVGs might not have a discernible effect on the investigated subpopulation within our carefully controlled experimental setting, our results cannot preclude that effects could be found in settings with higher ecological validity, in vulnerable subpopulations, or after more extensive VVG play.


Violent video games have often been accused of facilitating aggressive behaviour, in particular due to concerns that they could numb players toward real violence and therefore result in decreased empathy towards the pain of others. However, studies investigating these claims have often produced conflicting results, potentially due to methodological issues. For instance, work showing that violent games lead to emotional desensitization has often relied on testing participants immediately after a gaming session, which limits interpretations about prolonged impact. Many studies also compare gamers to people with no gaming experience, making it difficult to assess whether violent games decrease empathy, or whether less empathetic individuals are more likely to be drawn to this content. Lengersdorff et al. aimed to examine the long-term effects of violent video games using an experimental design that would bypass some of these limitations. A group of 89 young men with little gaming experience were recruited to play either a highly or non-violent version of the same game for seven hour-long sessions over two weeks. The way their brain reacted to violent images and processed other people's pain was assessed before and after this 'gaming training' using fMRI. The analyses showed no changes in these measures in volunteers who played the violent version of the game, suggesting that it had not numbed them to violence or affected their empathy. While experimental studies cannot fully capture the experiences of real-world gamers, the findings by Lengersdorff et al. represent a step towards resolving the scientific controversy surrounding the effects of violent games. Ultimately, a deeper understanding of how this type of media influences our emotions could help inform policymaking decisions about access to violent content.


Asunto(s)
Empatía , Juegos de Video , Humanos , Masculino , Teorema de Bayes , Estudios Prospectivos , Violencia/psicología , Agresión/psicología , Juegos de Video/psicología , Neuroimagen , Dolor
9.
Nat Nanotechnol ; 18(12): 1423-1429, 2023 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-37798564

RESUMEN

Strongly confined colloidal quantum dots have been investigated for low-cost light emission and lasing for nearly two decades. However, known materials struggle to combine technologically relevant metrics of low-threshold and long inverted-state lifetime with a material gain coefficient fit to match cavity losses, particularly under electrical excitation. Here we show that bulk nanocrystals of CdS combine an exceptionally large material gain of 50,000 cm-1 with best-in-class gain thresholds below a single exciton per nanocrystal and 3 ns gain lifetimes not limited by non-radiative Auger processes. We quantitatively account for these findings by invoking a strong bandgap renormalization effect, unobserved in nanocrystals to date, to the best of our knowledge. Next, we demonstrate broadband amplified spontaneous emission and lasing under quasi-continuous-wave conditions. Our results highlight the prospects of bulk nanocrystals for lasing from solution-processable materials.

10.
Front Psychiatry ; 14: 1256771, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37886114

RESUMEN

The notion of a connection between autism and music is as old as the first reported cases of autism, and music has been used as a therapeutic tool for many decades. Music therapy holds promise as an intervention for individuals with autism, harnessing their strengths in music processing to enhance communication and expression. While previous randomized controlled trials have demonstrated positive outcomes in terms of global improvement and quality of life, their reliance on psychological outcomes restricts our understanding of underlying mechanisms. This paper introduces the protocol for the Music for Autism study, a randomized crossover trial designed to investigate the effects of a 12-week music therapy intervention on a range of psychometric, neuroimaging, and biological outcomes in school-aged children with autism. The protocol builds upon previous research and aims to both replicate and expand upon findings that demonstrated improvements in social communication and functional brain connectivity following a music intervention. The primary objective of this trial is to determine whether music therapy leads to improvements in social communication and functional brain connectivity as compared to play-based therapy. In addition, secondary aims include exploring various relevant psychometric, neuroimaging, and biological outcomes. To achieve these objectives, we will enroll 80 participants aged 6-12 years in this international, assessor-blinded, crossover randomized controlled trial. Each participant will be randomly assigned to receive either music therapy or play-based therapy for a period of 12 weeks, followed by a 12-week washout period, after which they will receive the alternate intervention. Assessments will be conducted four times, before and after each intervention period. The protocol of the Music for Autism trial provides a comprehensive framework for studying the effects of music therapy on a range of multidimensional outcomes in children with autism. The findings from this trial have the potential to contribute to the development of evidence-based interventions that leverage strengths in music processing to address the complex challenges faced by individuals with autism. Clinical Trial Registration: Clinicaltrials.gov identifier NCT04936048.

11.
Turk J Ophthalmol ; 53(4): 257-260, 2023 08 19.
Artículo en Inglés | MEDLINE | ID: mdl-37602674

RESUMEN

A 69-year-old woman with bilateral primary open-angle glaucoma who underwent cataract extraction with intraocular lens implantation and excisional goniotomy with the Kahook Dual Blade (KDB; New World Medical, Rancho Cucamonga, CA, USA) in both eyes one year prior was referred for evaluation of significant visual acuity loss and pain in the left eye. On initial examination, intraocular pressure in the left eye was 3 mmHg and slit lamp examination revealed normal anterior chamber depth. Gonioscopy revealed a cyclodialysis cleft that was confirmed by anterior segment optical coherence tomography. Prominent chorioretinal folds suggestive of long-standing hypotony maculopathy were observed during fundoscopic examination. The cyclodialysis cleft, thought to be created inadvertently during the KDB goniotomy, resolved after three sessions of argon laser photocoagulation and the patient's symptoms and visual acuity partially improved.


Asunto(s)
Extracción de Catarata , Hendiduras de Ciclodiálisis , Glaucoma de Ángulo Abierto , Facoemulsificación , Trabeculectomía , Femenino , Humanos , Anciano , Facoemulsificación/efectos adversos , Glaucoma de Ángulo Abierto/complicaciones , Glaucoma de Ángulo Abierto/diagnóstico , Glaucoma de Ángulo Abierto/cirugía
12.
Clin Ophthalmol ; 17: 1557-1564, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37288002

RESUMEN

Minimally invasive glaucoma surgery (MIGS) has revolutionized glaucoma care with its favorable safety profile and ability to delay or minimize the need for traditional, bleb-based procedures. Microstent device implantation is a type of angle-based MIGS, which reduces intraocular pressure (IOP) through bypass of the juxtacanalicular trabecular meshwork (TM) and facilitation of aqueous outflow into the Schlemm's canal. Although there are limited microstent devices on the market, multiple studies have evaluated the safety and efficacy of iStent® (Glaukos Corp.), iStent Inject® (Glaukos Corp.), and Hydrus® Microstent (Alcon) in the treatment of mild-to-moderate open-angle glaucoma, with and without concurrent phacoemulsification. This review attempts to provide a comprehensive evaluation of injectable angle-based microstent MIGS devices in the treatment of glaucoma.

13.
Commun Biol ; 6(1): 645, 2023 06 27.
Artículo en Inglés | MEDLINE | ID: mdl-37369804

RESUMEN

Comparing the neural correlates of socio-cognitive skills across species provides insights into the evolution of the social brain and has revealed face- and body-sensitive regions in the primate temporal lobe. Although from a different lineage, dogs share convergent visuo-cognitive skills with humans and a temporal lobe which evolved independently in carnivorans. We investigated the neural correlates of face and body perception in dogs (N = 15) and humans (N = 40) using functional MRI. Combining univariate and multivariate analysis approaches, we found functionally analogous occipito-temporal regions involved in the perception of animate entities and bodies in both species and face-sensitive regions in humans. Though unpredicted, we also observed neural representations of faces compared to inanimate objects, and dog compared to human bodies in dog olfactory regions. These findings shed light on the evolutionary foundations of human and dog social cognition and the predominant role of the temporal lobe.


Asunto(s)
Mapeo Encefálico , Reconocimiento Visual de Modelos , Humanos , Perros , Animales , Lóbulo Temporal/diagnóstico por imagen , Encéfalo , Cara
15.
Nat Commun ; 14(1): 231, 2023 01 31.
Artículo en Inglés | MEDLINE | ID: mdl-36720865

RESUMEN

Navigating through crowded, dynamically changing environments requires the ability to keep track of other individuals. Grid cells in the entorhinal cortex are a central component of self-related navigation but whether they also track others' movement is unclear. Here, we propose that entorhinal grid-like codes make an essential contribution to socio-spatial navigation. Sixty human participants underwent functional magnetic resonance imaging (fMRI) while observing and re-tracing different paths of a demonstrator that navigated a virtual reality environment. Results revealed that grid-like codes in the entorhinal cortex tracked the other individual navigating through space. The activity of grid-like codes was time-locked to increases in co-activation and entorhinal-cortical connectivity that included the striatum, the hippocampus, parahippocampal and right posterior parietal cortices. Surprisingly, the grid-related effects during observation were stronger the worse participants performed when subsequently re-tracing the demonstrator's paths. Our findings suggests that network dynamics time-locked to entorhinal grid-cell-related activity might serve to distribute information about the location of others throughout the brain.


Asunto(s)
Encéfalo , Sistemas de Computación , Humanos , Cuerpo Estriado , Corteza Entorrinal , Cabeza
16.
J Am Chem Soc ; 145(1): 732-744, 2023 Jan 11.
Artículo en Inglés | MEDLINE | ID: mdl-36538761

RESUMEN

Control over the populations of singlet and triplet excitons is key to organic semiconductor technologies. In different contexts, triplets can represent an energy loss pathway that must be managed (i.e., solar cells, light-emitting diodes, and lasers) or provide avenues to improve energy conversion (i.e., photon upconversion and multiplication systems). A key consideration in the interplay of singlet and triplet exciton populations in these systems is the rate of intersystem crossing (ISC). In this work, we design, measure, and model a series of new electron acceptor molecules and analyze them using a combination of ultrafast transient absorption and ultrafast broadband photoluminescence spectroscopies. We demonstrate that intramolecular triplet formation occurs within several hundred picoseconds in solution and is accelerated considerably in the solid state. Importantly, ISC occurs with sufficient rapidity to compete with charge formation in modern organic solar cells, implicating triplets in intrinsic exciton loss channels in addition to charge recombination. Density functional theory calculations reveal that ISC occurs in triplet excited states characterized by local deviations from orbital π-symmetry associated with rotationally flexible thiophene rings. In disordered films, structural distortions, therefore, result in significant increases in spin-orbit coupling, enabling rapid ISC. We demonstrate the generality of this proposal in an oligothiophene model system where ISC is symmetry-forbidden and show that conformational disorder introduced by the formation of a solvent glass accelerates ISC, outweighing the lower temperature and increased viscosity. This proposal sheds light on the factors responsible for facile ISC and provides a simple framework for molecular control over spin states.

17.
J Ophthalmic Vis Res ; 18(4): 445-451, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-38250230

RESUMEN

Purpose: To report the development of malignant epiretinal membrane after radiation of ciliary body melanoma. Case Report: A 65-year-old woman was referred for evaluation of a ciliary body tumor in her right eye. On examination, a pigmented ciliary body tumor, displacing the iris anteriorly, was visible superotemporally and ultrasound biomicroscopy revealed a large solid ciliary body tumor. She was diagnosed with ciliary body melanoma and treated with proton beam radiation. Over the following 29 months, the treated tumor regressed but optical coherence tomography (OCT) showed the development of a dense epiretinal membrane. Enucleation was performed and histopathological examination showed viable melanoma cells in the vitreous cavity with sheet-like growth of viable spindle melanoma cells on the epiretinal surface. Conclusion: The development of a pigmented epiretinal membrane in eyes with uveal melanoma should raise the possibility of a malignant epiretinal membrane.

18.
Mayo Clin Proc Innov Qual Outcomes ; 6(6): 618-635, 2022 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-36405987

RESUMEN

Glaucoma is the leading cause of blindness throughout the world (after cataracts); therefore, general physicians should be familiar with the diagnosis and management of affected patients. Glaucomas are usually categorized by the anatomy of the anterior chamber angle (open vs narrow/closed), rapidity of onset (acute vs chronic), and major etiology (primary vs secondary). Most glaucomas are primary (ie, without a contributing comorbidity); however, several coexisting ophthalmic conditions may serve as the underlying etiologies of secondary glaucomas. Chronic glaucoma occurs most commonly; thus, regular eye examinations should be performed in at-risk patients to prevent the insidious loss of vision that can develop before diagnosis. Glaucoma damages the optic nerve and retinal nerve fiber layer, leading to peripheral and central visual field defects. Elevated intraocular pressure (IOP), a crucial determinant of disease progression, remains the only modifiable risk factor; thus, all current treatments (medications, lasers, and operations) aim to reduce the IOP. Pharmacotherapy is the usual first-line therapy, but noncompliance, undesirable adverse effects, and cost limit effectiveness. Laser and surgical treatments may lower IOP significantly over long periods and may be more cost effective than pharmacotherapy, but they are plagued by greater procedural risks and frequent treatment failures. Traditional incisional procedures have recently been replaced by several novel, minimally invasive glaucoma surgeries with improved safety profiles and only minimal decreases in efficacy. Minimally invasive glaucoma surgeries have dramatically transformed the surgical management of glaucoma; nevertheless, large, randomized trials are required to assess their long-term efficacy.

20.
Proc Natl Acad Sci U S A ; 119(43): e2212343119, 2022 10 25.
Artículo en Inglés | MEDLINE | ID: mdl-36227945

RESUMEN

The natural black-brown pigment eumelanin protects humans from high-energy UV photons by absorbing and rapidly dissipating their energy before proteins and DNA are damaged. The extremely weak fluorescence of eumelanin points toward nonradiative relaxation on the timescale of picoseconds or shorter. However, the extreme chemical and physical complexity of eumelanin masks its photoprotection mechanism. We sought to determine the electronic and structural relaxation pathways in eumelanin using three complementary ultrafast optical spectroscopy methods: fluorescence, transient absorption, and stimulated Raman spectroscopies. We show that photoexcitation of chromophores across the UV-visible spectrum rapidly generates a distribution of visible excitation energies via ultrafast internal conversion among neighboring coupled chromophores, and then all these excitations relax on a timescale of ∼4 ps without transferring their energy to other chromophores. Moreover, these picosecond dynamics are shared by the monomeric building block, 5,6-dihydroxyindole-2-carboxylic acid. Through a series of solvent and pH-dependent measurements complemented by quantum chemical modeling, we show that these ultrafast dynamics are consistent with the partial excited-state proton transfer from the catechol hydroxy groups to the solvent. The use of this multispectroscopic approach allows the minimal functional unit in eumelanin and the role of exciton coupling and excited-state proton transfer to be determined, and ultimately reveals the mechanism of photoprotection in eumelanin. This knowledge has potential for use in the design of new soft optical components and organic sunscreens.


Asunto(s)
Protones , Protectores Solares , Catecoles , Humanos , Melaninas , Solventes
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