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Boron, the element which is in close proximity with carbon in the periodic table has been hypothesized to produce diverse two‐dimensional structures that differ from well‐studied 2D materials. Icosahedron B12$$ {\mathcal{B}}_{12} $$, the monomers of which form the crystalline boron structure, appears as a recurring pattern in the chemistry of boron compounds, elemental boron and boron‐rich materials, functions as a building block in a majority of boron allotropes. The topological study of the icosahedral sheets is a necessary field to be investigated for the effective analysis and characterization of its physico‐chemical attributes without undertaking time‐consuming experimental research. The topological descriptors being expressed as numerical values enable scientists to compare and correlate data, which can be applied to quantitative structure‐activity relationships and quantitative structure‐property relationships modeling. In this study, various degree based molecular descriptors of the crystal boron icosahedral α$$ \alpha $$ sheet Bα(a,b)$$ {\mathcal{B}}_{\alpha}\left(\mathfrak{a},\mathfrak{b}\right) $$ has been formulated from a two‐dimensional lattice perspective using the 필‐polynomial approach. To establish the significance of these descriptors in the study of chemical attributes, an efficient linear regression modeling has also been performed, enabling the prediction of properties of several other boron sheets. [ABSTRACT FROM AUTHOR]

The application of graph theory to metacommunity ecology allows a deeper analysis of the effect of network structure on diversity patterns. Here, we set out to test the role of network centrality metrics and environmental characteristics in diversity patterns of pond macroinvertebrate metacommunities. We tested two approaches to construct the networks: one used the percolation distance, whereas the other was based on a community‐contingent distance. The role of each patch within the network was then analyzed using its centrality value. Later, we analyzed the relationships between the macroinvertebrate diversity and centrality metrics for four study sites. The calculated diversity metrics cover different facets of biodiversity at two scales: pond and pondscape. Environmental characteristics of the studied ponds were also included. All relationships were tested considering the entire macroinvertebrate dataset, but also differentiated by dispersal mode (i.e., active vs. passive) and considering the two types of network approaches analyzed. The results were mostly consistent when comparing the network approaches used. Centrality metrics tended to be positively related to alpha and negatively to beta diversity. Environmental uniqueness showed a positive effect on beta diversity metrics, regardless of the dispersal mode. We only observed a weak negative relationship between eutrophication and species richness of active dispersers. Pond size showed a positive effect on both alpha and beta diversity, but was detected more frequently on alpha diversity metrics. We could not find evidence for a clear negative effect of habitat degradation on diversity. We found a greater importance of environmental characteristics versus the centrality metrics for both alpha and beta diversity of active dispersers, while a combination of their contributions for passive dispersers. An unexpected importance of centrality was observed for alpha diversity of passive dispersers. Using empirical data, we demonstrate that the centrality of a patch in an undirected network affects diversity regardless of the approach used to construct the networks, with a higher influence at local scale regardless of the dispersal mode. This study broadens knowledge of the relationships between environmental features and network centrality, demonstrating the important role of centrality as a determinant of diversity in metacommunities. [ABSTRACT FROM AUTHOR]

In the current era of technological advancement, dendrimers have been in high demand as the fundamental component in the field of drug design. For better efficacy, scientists have been working intensely to produce potentially beneficial dendrimer molecules. Mathematical chemistry has a lot to offer with effective tools like molecular descriptors and functions that can forecast compound molecular features. Topological descriptors, being numerical invariants associated with a chemical compound, have the potential to correlate chemical structure with different physical attributes, chemical reactivity, or biological activity. By incorporating these descriptors in QSAR and QSPR modeling, it is possible to predict a variety of physicochemical attributes and bioactivities. Hence, the main objective of the study is to obtain the distance‐based molecular descriptors of triazine‐based dendrimer and subsequently generate linear models for their chemical properties using regression analysis. This linear model can predict the properties of succeeding generations, avoiding the necessity for time‐consuming laboratory experimental trials. [ABSTRACT FROM AUTHOR]

The role of dendrimers is getting updated and grabbing immense attention in many fields. Dendrimers are used in a broad spectrum, in specific, it is widely utilized in drug delivery, for targeted carrier and specific action. Also, in drug catalysis, it improves the solubility of poorly soluble drugs and increases the stability of active ingredients within the cores. Many researchers are interested in developing new dendrimers by using various compounds. π‐conjugated dendrimers via truxenes and thienylethynylene units, are considered a promising material in the field of medicinal chemistry, bio‐organic, and environmental sciences. In QSAR/QSPR, the structural analysis of chemical compounds is examined by topological descriptors. In this article, the various distance‐based topological indices such as Wiener, Szeged, and Mostar of gradient star‐persistent π‐conjugated dendrimers are determined. Since gradient star‐persistent π‐conjugated dendrimers have odd cycles, the usual cut method is not applicable, therefore we use a new concept, the quotient of quotient graph to determine the numerical expression of various indices. An analysis of linear regression reveals that degree‐based topological descriptors predict better physicochemical properties. [ABSTRACT FROM AUTHOR]

Ecological recovery following restoration is typically evaluated using metrics based on species diversity and composition. However, increasing evidence suggests the success of long‐term ecological recovery increases when more complex attributes such as biotic interaction networks are targeted. In created lagoons, the influence of nearby habitats can generate early similarities in the community structure, but communities often diverge from surrounding water bodies at later successional stages. These changes have been attributed to the effect of biotic interactions, but few studies have tested this assumption. Here, we analyze the zooplankton community recovery after the creation of new lagoons in a Mediterranean coastal wetland using beta diversity approaches and mixed graphical models to infer interaction networks from abundance data. Increasing differences in the community structure between new and old lagoons were detected the second year after their creation. The overall interaction network was more complex in new than in old lagoons. Interestingly, the network structure in old lagoons increased its complexity during the third and fourth years after restoration. The creation of new lagoons with overall milder environmental conditions contributed to a greater differentiation of the zooplankton community structure between new and old lagoons. Moreover, our results suggest that the creation of a heterogeneous and more connected landscape can increase the interaction network in newly created and pre‐existing habitats, even if environmental conditions remain unchanged. We show how the inclusion of interaction networks for the monitoring of ecosystem recovery reflects unique facets of community complexity, otherwise overlooked when targeting diversity metrics alone. [ABSTRACT FROM AUTHOR]

Fossil fuel divestment movements have gained momentum since 2011, aimed at ending fossil fuel use and a move toward a cleaner, affordable, and sustainable energy system, for business and society. The present study investigates the direct impact of fossil fuel divestment announcements on stock prices of firms listed on the United States' stock exchanges. Using an event study and guided by the United Nation's sustainable development goals (SDGs), we test the effects of 116 divestments announcements between 2014 and 2019 on 51 publicly traded fossil fuel companies. Our results suggest that there is a negative effect of these announcements on fossil fuel firm stock prices. Also, we find that the type of fossil fuel firm (coal or oil and gas), the type of divestment (partial, coal only, or full), the timing of the announcement, and the size of the divesting investor have some explanatory power in relation to the (cumulative) abnormal returns following the divestment announcements. While the negative impact on stock prices is not surprising, the reaction from the divested firms after such large divestitures is not consistent with what may be expected, given past reactions to divestitures seeking to achieve different social goals. Given the SDGs, it seems clear why investors are divesting themselves from fossil fuel firms, but why has the reaction to the 116 divestments led to very little change in the way these publicly traded fossil fuel firms do business given their direct and growing impacts on society? We conclude the study with some suggestions for future research. [ABSTRACT FROM AUTHOR]

Disturbances, such as wildfires, are one of the main drivers of biodiversity dynamics, and their frequency and intensity are expected to increase due to global change. Such disturbances generate a mosaic of affected and unaffected patches that change landscape structure and, consequently, metacommunity networks. Therefore, to fully understand the consequences of such disturbances, a landscape perspective is required. In 2012, a wildfire burned 13 000 hectares in the NE Iberian Peninsula affecting a pond macroinvertebrate metacommunity. Communities were highly resilient to this disturbance, recovering after one hydroperiod. Their resilience was related to dispersal, being lower in species with weak dispersal abilities than those with strong dispersal abilities. This suggested that the metacommunity network played a major role in defining system resilience. In this context, we introduced a theoretical analysis based on this network in which we evaluated metacommunity resilience across several gradients of disturbance size and intensity incorporating species dispersal ability. Our study supports the empirical observation of a highly resilient metacommunity but also reveals that increased disturbance regimes might lead to a collapse of this resilience. Disturbance size and intensity interacted to determine the community recovery rate, which was high when both variables were low. Nevertheless, the transition from high to low resilience was sharp and depended on species dispersal. Diversity recovery was mostly driven by disturbance intensity, abruptly collapsing with its rise. This response highlighted the qualitative difference in the effect of size and intensity. These results not only illustrate the mechanisms shaping the studied metacommunity but also more generally stress the strong role of metacommunity mechanisms and landscape structure in biodiversity resilience. Finally, this study highlights the importance of using theoretical approaches rooted in empirical data to determine metacommunity dynamics and the need to preserve and build connected and heterogeneous landscapes to address future disturbance scenarios. [ABSTRACT FROM AUTHOR]

Aside from structural indicators, functional indicators have been suggested as a tool for assessing the health of transitional water ecosystems. The aim of this study was to assess the potential for the use of plant litter decomposition as a functional indicator of ecosystem health in coastal lagoons.A field experiment was conducted to assess the decomposition rate of Ruppia maritima enclosed in coarse and fine mesh litterbags and incubated in 10 Mediterranean coastal lagoons that conform to a gradient of ecological status produced by anthropogenic impacts as determined by a structural quality index.The microbial decomposition rate in fine mesh litterbags increased linearly along the ecological gradient. However, this relationship was not observed for the overall decomposition rate in coarse mesh bags.Decomposition rates in coarse mesh bags were negatively related to macroinvertebrate diversity, indicating that, in transitional habitats, such as coastal lagoons, high biodiversity is not a prerequisite for successful ecosystem functioning.The results suggest that functional indicators, such as the microbial litter decomposition process, should be used in addition to structural ones to detect anthropogenic‐derived environmental perturbations in coastal lagoons. [ABSTRACT FROM AUTHOR]

The Mediterranean region has historically been affected by wildfires. However, studies addressing wildfire impacts have traditionally focused first on terrestrial systems and second on lotic systems. This bias has left a gap in knowledge related to wildfire effects on some of the emblematic habitats of the Mediterranean region such as temporary ponds.We hypothesise that temporary ponds will experience indirect consequences of wildfires like those of other aquatic systems (e.g. nutrient increases or trophic alterations). However, the fact that temporary ponds are dry during the summer, when most wildfires occur, could add a new path of disturbance such as an impact on organisms aestivating in the pond sediment due to their direct burning. Based on these hypotheses, the present study analyses wildfire impacts on faunal communities adapted to temporality, focusing on species traits related to expected indirect and direct impacts (i.e. dispersal ability, life history or feeding habits).We took advantage of a wildfire (summer 2012) that partially affected a Mediterranean temporary pond network, comparing the environmental and the faunal community responses from before and after the wildfire, and between the burned and unburned ponds during the subsequent hydroperiod.As hypothesised, our results indicated different wildfire effects. First, changes in abundances of some trophic groups from before and after the wildfire but also strong fluctuations at the beginning of the hydroperiod between burned and unburned ponds. Second, a decrease in abundance of organisms that remain in the pond sediment during drought in burned ponds, being probably affected directly by the wildfire.Only one hydroperiod appears to be sufficient for burned ponds to recover their similarity to unburned ponds, which highlights the high resilience of these communities. Despite their resilience, these communities could become compromised in the future since global change scenarios predict increase wildfire frequency and intensity in the Mediterranean region. [ABSTRACT FROM AUTHOR]

Summary: Animal bites are a serious public health issue, and prevention strategies have been consistently documented worldwide. The aim of this study was to characterize human anti‐rabies treatment in 11 counties of the Salgado microregion, Pará state, Brazil, which borders the Bragantina microregion, where exposures of human rabies were reported in 2004 and 2005. A descriptive retrospective study was conducted using anti‐rabies treatment notifications registered in the Information System for Notifiable Diseases (SINAN) database of the State Department of Public Health of Pará (SESPA) from January 2000 to December 2014. In this period, 13,403 exposures were reported, with a growing annual trend (Y = 68.571x + 344.96). The years 2012 and 2013 presented the highest exposure incidence. Salinópolis was the county with the highest average annual incidence per 10,000 persons (62.83), followed by São João de Pirabas (43.28) and São Caetano de Odivelas (41.27). Most patients were males (59.6%) and were 1–19 years old (48.7%). The main species involved in aggressions were dogs (74.1%), followed by bats (13.1%) and cats (7.4%). Biting was the most common kind of exposure, mostly on the lower limbs (39.6%). This study shows that aggression by bats was the second most common cause of demand for the service in the region for the past 14 years. The low quality of records may increase the difficulty of rabies surveillance in Pará. [ABSTRACT FROM AUTHOR]

Trophic cascade studies have so far mostly focused on changes in the abundance, biomass, or average size of prey and predators. In contrast, individual size-based interactions, playing a key role in the trophic structure and functioning of aquatic ecosystems, have been less explored., We conducted a 3-month in situ experiment in Lake Mývatn, Iceland, with two fish treatments (with and without fish, Gasterosteus aculeatus). After the first month of the experiment, Anabaena blooms appeared in the lake. We studied the effects of fish predation and occurrence of cyanobacteria blooms on the individual size structure (i.e. the distribution of the number of organisms over a size range) of zooplankton and phytoplankton. We also assessed the potential consequences for trophic transfer efficiency ( TTE) (measured as the predator to prey biomass ratio) in the planktonic food web., Our results showed that fish predation and cyanobacteria bloom had a negative relationship with size diversity of zooplankton, which became dominated by small-sized individuals in both cases. The phytoplankton size diversity changed over time particularly due to the blooming of large-sized Anabaena, and its increase was apparently mainly driven by changes in resources., Low zooplankton size diversity related to fish predation reduced TTE, particularly in the enclosures with fish. This may be because low zooplankton size diversity represents a lower partition of resources among consumers, thereby decreasing the trophic energy transfer. With the occurrence of Anabaena bloom, high phytoplankton size diversity coincided with a lower energy transfer in all enclosures likely due to reduced zooplankton grazing when large-sized colony-forming Anabaena dominated., In conclusion, our results indicate that both top-down and bottom-up forces significantly influence the size structure of planktonic communities. The changes in size structure were related to shifts in the energy transfer efficiency of the Lake Mývatn food web. Thus, our study underpins the importance of taking into account size-based interactions in the study of trophic cascades, particularly in a warming climate where strong planktivorous fish predation and frequent cyanobacteria blooms may occur. [ABSTRACT FROM AUTHOR]

Social acceptance has become a key consideration for promoters, government officials and citizens when instituting new energy infrastructures and technologies. Often theorized in normative terms, it is not clear whether and when social acceptance matters. This article explores the rollout of smart meters in Quebec, which proceeded despite significant opposition from municipalities, community groups and unions. Drawing on core concepts from punctuated equilibrium theory-policy monopoly, policy venue, policy image-we argue that this opposition had no policy venue to express its grievances. Quebec's electricity sector, with a stable policy environment controlled by a policy monopoly and buttressed by a strong policy image, provided few opportunities to expand the conflict. We conclude from this analysis that public administrators should consider power when measuring social acceptance in political processes. [ABSTRACT FROM AUTHOR]

A method for the measurement of the size diversity based on the classical Shannon-Wiener expression was proposed as a proxy of the shape of the size distribution. The summatory of probabilities of a discrete variable (such as species relative abundances) in the original Shannon-Wiener expression was substituted by an integral of the probability density function of a continuous variable (such as body size). Here, we propose an update of this method by including the measurement of the size e-evenness, just dividing the exponential of the size diversity by its possible maximum for a given size range. Assuming a domain of the size range of (0,∞), for a given logarithmic mean ( [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the HLA- A, HLA- B and HLA- DRB1 allele groups frequencies in a population of 1559 volunteer bone marrow donors from the northwestern region of São Paulo State grouped according to ethnicity. An additional objective was to compare the allele frequencies of the current study with data published for other Brazilian populations. The allele groups were characterized by the PCR-r SSO method using Luminex® technology. Twenty HLA- A, 32 HLA- B and 13 HLA- DRB1 allele groups were identified. The most common allele groups in European descent and mixed African and European descent samples were HLA- A*02, HLA- B*35 and HLA- DRB1*13, while HLA- A*02, HLA- B*35 and HLA- DRB1*11 were more common in African descent samples. The HLA- A*23, HLA- A*36, HLA- B*58 and HLA- B*81 allele groups were more common in sample from African descent than European descent, and the HLA- DRB1*08 was more common in mixed African and European descent than in European descent. Allele group frequencies were compared with samples from other Brazilian regions. The HLA- A*30 and HLA- A*23 were more common in this study than in the populations of Rio Grande do Sul and Paraná; and the HLA- A*01, HLA- B*18, HLA- B*57 and HLA- DRB1*11 were more common in this study than in the population of Piauí. The least frequent allele groups were HLA- A*31, HLA- B*15, HLA- B*40 and HLA- DRB1*08 for the population of Piauí, HLA-A*01 and HLA- A*11 for Parana, HLA- A*02 and - A*03 for Rio Grande do Sul and HLA- DRB1*04 for Paraná, Rio Grande do Sul and Piauí. These data provide an overview on the knowledge on HLA diversity in the population of the northwestern region of São Paulo State and show that the genes of this system are useful to distinguish different ethnic groups. [ABSTRACT FROM AUTHOR]

We sought to identify environmental factors influencing crustacean zooplankton species richness in brackish lagoons and to elucidate whether crustacean zooplankton species richness and trophic structure of brackish lagoons differ among two regions with contrasting temperatures. We sampled 35 and 42 brackish lagoons (salinity ranging from 0.3 to 55‰) in Mediterranean Catalonia (NE Spain) and northern-temperate Denmark, respectively. No significant differences were found in total crustacean zooplankton species richness or cladoceran richness between the climatic regions. Calanoid richness was higher in Denmark than in Catalonia, while cyclopoid richness was higher in Catalonia. Salinity was the most important variable associated with zooplankton species richness in both regions, richness of total zooplankton species, cladocerans and cyclopoids being negatively related with salinity. In both regions, a shift occurred from dominance of large filter feeding cladoceran species at low salinities to copepods and small cladoceran species at higher salinities. Cladoceran richness increased with increasing total phosphorus, but was not influenced by total nitrogen or chlorophyll-a. Trophic structure in Mediterranean brackish lagoons showed a more pronounced seasonal variation than in north temperate brackish lagoons. Our results imply that the indirect effects of climate warming, such as changes in salinity and hydrology, will have a larger impact on brackish lagoon ecosystems than the increase in temperature per se. [ABSTRACT FROM AUTHOR]

The article presents a study on the ecological status of Ter Vell, an eutrophic Mediterranean coastal lagoon in Northeast Iberian Peninsula after being flooded by excessive water from the irrigation during the past decades, and other man-made changes of its hydrological regime. It analyzes whether the hydrological changes caused by management actions have affected the lagoon's status. The suitability of several physiochemical and biological indicators for the assessment of the ecological status of this kind of coastal ecosystem are also presented. Methods involved and the indicators used in the study are also discussed.

Background. The aim of this study was to examine which factors are related to patient delay in a cohort of consecutive patients with pharyngeal cancer and oral cancer and to determine whether the different stages of patient delay (ie, appraisal, illness, behavioral, and scheduling) were related to different tumor stages. Methods. Before treatment, 55 patients with pharyngeal cancer and 134 patients with oral cancer were interviewed about their prediagnostic period. To verify the data, a questionnaire was sent to the general practitioner and/or dentist and a close relative. Results. Patients with a delay of more than 30 days were significantly more often diagnosed with late-stage (T3–T4) disease (pharynx, p = .01, odds ratio [OR] = 4.5; oral, p = .01, OR = 3.2). No sociodemographic characteristics were associated with patient delay. Conclusions. Prolonged patient delay was associated with late-stage disease for both patients with pharyngeal cancer and patients with oral cancer. Although for most patients the symptoms are vague or might look like a common cold or infection, the general public should be better informed about tumor symptoms. This may enhance earlier visits to a health care professional. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX–XXX, 2005 [ABSTRACT FROM AUTHOR]

We assessed the importance of temperature, salinity, and predation for the size structure of zooplankton and provided insight into the future ecological structure and function of shallow lakes in a warmer climate. Artificial plants were introduced in eight comparable coastal shallow brackish lakes located at two contrasting temperatures: cold-temperate and Mediterranean climate region. Zooplankton, fish, and macroinvertebrates were sampled within the plants and at open-water habitats. The fish communities of these brackish lakes were characterized by small-sized individuals, highly associated with submerged plants. Overall, higher densities of small planktivorous fish were recorded in the Mediterranean compared to the cold-temperate region, likely reflecting temperature-related differences as have been observed in freshwater lakes. Our results suggest that fish predation is the major control of zooplankton size structure in brackish lakes, since fish density was related to a decrease in mean body size and density of zooplankton and this was reflected in a unimodal shaped biomass-size spectrum with dominance of small sizes and low size diversity. Salinity might play a more indirect role by shaping zooplankton communities toward more salt-tolerant species. In a global-warming perspective, these results suggest that changes in the trophic structure of shallow lakes in temperate regions might be expected as a result of the warmer temperatures and the potentially associated increases in salinity. The decrease in the density of large-bodied zooplankton might reduce the grazing on phytoplankton and thus the chances of maintaining the clear water state in these ecosystems. [ABSTRACT FROM AUTHOR]

1.According to the European Water Framework Directive (2000/60/CE) tools are required to evaluate wetland ecological quality. In this context, a biological index to evaluate water quality (QAELS) is proposed for Mediterranean wetlands in Catalunya (NE Iberian peninsula).2.The study was carried out in 99 shallow lentic ecosystems, situated below 800 m a.s.l. and with a maximum depth of less than 6 m. At each sampling point, a range of water parameters was measured (temperature, conductivity, pH, dissolved oxygen, chlorophyll a, dissolved nutrients and total nutrients) and data were gathered on invertebrate taxon composition (collected with a dip‐net of 250 µm mesh size).3.A previous classification of wetlands in that area was required to obtain QAELS. The QAELS index is obtained by: (1) the relative abundance of each microcrustacean taxon (Cladocera, Copepoda and Ostracoda) weighted by an ecological quality requirement coefficient, which is obtained for each taxon by means of partial canonical correspondence analysis (ACCO index); and (2) the taxonomic richness of crustaceans and aquatic insects (RIC index).4.Several taxonomic resolutions were also tested in order to determine the simplest identification level that gives acceptable results in further applications of the QAELS index. It is concluded that the composition of microcrustacean assemblages (ACCO index) is useful for assessing the water quality of Mediterranean wetlands.5.The RIC index improves the relationship of the QAELS index to water quality variables, avoiding possible anomalous values that could be obtained when using the ACCO index alone. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The aim was to determine the effects of dulaglutide, a synthetic once-weekly, injectable human glucagon-like peptide 1 analogue that lowers blood glucose, body weight, appetite and blood pressure, on cardiovascular outcomes. People with type 2 diabetes, aged ≥50 years, with glycated haemoglobin (HbA1c) ≤9.5%, and either a previous cardiovascular event, evidence of cardiovascular disease or ≥2 cardiovascular risk factors were randomly allocated to a weekly subcutaneous injection of either dulaglutide (1.5 mg) or placebo and followed within the ongoing Researching cardiovascular Events with a Weekly INcretin in Diabetes (REWIND) trial every 3 to 6 months. The primary cardiovascular outcome is the first occurrence of the composite of cardiovascular death or non-fatal myocardial infarction or non-fatal stroke. Secondary outcomes include each component of the primary composite cardiovascular outcome, a composite clinical microvascular outcome comprising retinal or renal disease, hospitalization for unstable angina, heart failure requiring hospitalization or an urgent heart failure visit, and all-cause mortality. Follow-up will continue until the accrual of 1200 confirmed primary outcomes. Recruitment of 9901 participants (mean age 66 years, 46% women) occurred in 370 sites located in 24 countries over a period of 2 years. The mean duration of diabetes was 10 years, mean baseline HbA1c was 7.3%, and 31% had prior cardiovascular disease. The REWIND trial's international scope, high proportion of women, high proportion of people without prior cardiovascular disease and inclusion of participants whose mean baseline HbA1c was 7.3% suggests that its cardiovascular and safety findings will be directly relevant to the typical middle-aged patient seen in general practice throughout the world., (© 2017 John Wiley & Sons Ltd.)

The centre of the human lens, which is composed of proteins that were synthesized prior to birth, is an ideal model for the evaluation of long-term protein stability and processes responsible for the degradation of macromolecules. By analysing the sequences of peptides present in human lens nuclei, characteristic features of intrinsic protein instability were determined. Prominent was the cleavage on the N-terminal side of serine residues. Despite accounting for just 9% of the amino acid composition of crystallins, peptides with N-terminal Ser represented one-quarter of all peptides. Nonenzymatic cleavage at Ser could be reproduced by incubating peptides at elevated temperatures. Serine residues may thus represent susceptible sites for autolysis in polypeptides exposed to physiological conditions over a period of years. Once these sites are cleaved, other chemical processes result in progressive removal or 'laddering' of amino acid residues from newly exposed N- and C-termini. As N-terminal Ser peptides originated from several crystallins with unrelated sequences, this may represent a general feature of long-lived proteins., (© 2012 The Authors. Aging Cell © 2012 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.)