Natural Counterparts Research Articles

Innovations and Insights in Superhydrophobicity: Learning from Nature to Surpass It

Abstract. Superhydrophobic surfaces, inspired by natural examples, have emerged as a promising area of research due to their unique properties. This paper reviews the characteristics and challenges of creating surfaces that can exceed the capabilities of natural counterparts. Key aspects include surface tension, contact angle, and morphology, with a focus on natural models such as lotus leaves and gecko feet. The paper highlights knowledge gaps in durability and manufacturing, and discusses design challenges in achieving roughness, hierarchy, and balance between hydrophobicity and durability. Methods for enhancing durability, such as chemical and roughness restoration, are explored, alongside the potential of AI in optimizing material and design choices. The paper concludes with recommendations for future research directions in the field.

Synthesis of 13β- and 13α-epimers of 3-hydroxy-17-hydroxymethylestra-1,3,5(10)-triene and considerations on their hormonal and antiproliferative potency

Starting from 3-methoxyestra-1,3,5(10),16-tetraene-17-carbaldehydes of natural (13β) and epimeric (13α) series, a series of isomeric 3-hydroxy-17-hydroxymethylestra-1,3,5(10)-trienes, including those containing 16α,17α-annulated cyclopropane and cyclohexane ring D’, were prepared using the Corey-Chaykovsky and Diels-Alder reactions followed by reduction-demethylation with diisobutylaluminum hydride and hydrogenation. Target compounds showed antiproliferative effects on MCF-7 breast cancer cells to varying degrees superior to that on MCF-10A cells, in low micromolar concentrations. The ERα-mediated luciferase reporter gene assay demonstrated that obtained steroids without an additional carbocycle or with a cyclopropane 16α,17α-annulated carbocycle are effective ERα activators. In this test, steroids of the natural configuration showed high activity at both 10 nM and 100 nM concentrations, whereas 13α-steroids showed a strong dose-dependent effect, surpassing their natural counterparts at a concentration of 100 nM. The 13β-steroid bearing additional 16α,17α-cyclohexane ring had low activity in the test. A simple docking approach using AutoDock Vina was used as a test for a preliminary assessment of the estrogenicity of the compounds. The scope of its applicability and limitations were shown using examples of synthesized molecules.

Emergent behaviors of buckling-driven elasto-active structures

Active systems of self-propelled agents, e.g., birds, fish, and bacteria, can organize their collective motion into myriad autonomous behaviors. Ubiquitous in nature and across length scales, such phenomena are also amenable to artificial settings, e.g., where brainless self-propelled robots orchestrate their movements into spatial-temporal patterns via the application of external cues or when confined within flexible boundaries. Like their natural counterparts, these approaches typically require many units to initiate collective motion, so controlling the ensuing dynamics is challenging. Here, we demonstrate a simple mechanism that leverages nonlinear elasticity to tame near-diffusive motile particles in forming structures capable of directed motion and other emergent behaviors. Our elasto-active system comprises two centimeter-sized self-propelled microbots connected with elastic beams. These microbots exert forces that suffice to buckle the beam and set the structure in motion. We first rationalize the physics of the interaction between the beam and the microbots. Then we use reduced-order models to predict the interactions of our elasto-active structures with boundaries, e.g., walls and constrictions, and demonstrate how they can exhibit remarkable emergent behaviors such as maze navigation. These findings demonstrate that allowing and understanding changes in body morphology can enhance the capabilities of active matter systems and enable the design of robotic materials capable of space exploration, adaptation, and complex interactions with their surrounding environment.

Anti-PD-L1 chimeric antigen receptor natural killer cell: Characterization and functional analysis.

Like their natural counterparts, chimeric antigen receptor-engineered cells are prone to suppression by inhibitory signals, such as PD-L1, expressed by tumors or suppressor cells in the tumor microenvironment. Consequently, they become impaired, resulting in immune cell exhaustion, tumor progression, and resistance to other therapies. In this study, we developed an anti-PD-L1-CAR NK cell with efficient activity and a notable PD-L1-specific response toward tumor cell lines. The degranulation assay demonstrated that CD107a frequencies between the PD-L1med and PD-L1high groups and between Herceptin-treated and non-treated groups were not statistically different. Further investigation into NK cell characterization, considering different markers such as CD57, KIR2D, and CD25, revealed that the majority of the population are activated expanding NK cells. At the same time, immune checkpoint inhibitors, including PD-1, PD-L1, and LAG-3, showed increased levels following activation and expansion. Regarding the efficient functional activity of PD-L1-CAR NK cells and the instinctive receptor balance-based response of NK cells, this observation could point to the inhibition of NK cell overactivation or even higher cytotoxicity and cytokine production rather than exhaustion, especially in the case of healthy NK cells. These findings can contribute to a better understanding of the potential and challenges of using primary NK cells for CAR-NK cell therapy.

House sparrows do not show a diel rhythm in double-strand DNA damage in erythrocytes.

DNA damage can be caused by a number of intrinsic and extrinsic factors. A recent study showed that free-living house sparrows (Passer domesticus) have higher DNA damage in the summer than the winter across five different tissues. This result was consistent when house sparrows were brought into captivity and exposed to comparable light cycles, with all other variables held constant. These results generated two hypotheses: (1) seasonal variation in DNA damage is related to circadian regulation and (2) seasonal variation in DNA damage is related to the total number of active hours. To investigate these hypotheses, we first quantified erythrocyte DNA damage in wild-caught house sparrows held in captivity on a 12L:12D light cycle at six points during the day to assess a diel or circadian rhythm but did not find one. We then performed a resonance experiment, in which birds experienced unnatural light cycles, and compared DNA damage in birds held on 6L:6D and 4.5L:7.5D resonance light cycles with their natural counterparts, 12L:12D and 9L:15D, respectively. We assessed corticosterone levels and DNA damage in blood before and after the resonance light cycles and DNA damage in abdominal fat, hippocampus, hypothalamus, and liver after the resonance light cycles. While our second experiment was not able to effectively test our hypotheses, we were able to demonstrate some interesting patterns. Throughout the resonance experiment, baseline corticosterone and testes size increased, consistent with the birds being photostimulated and preparing to breed. Surprisingly, the direction of change of DNA damage throughout the resonance photoperiod differed with tissue, which is not consistent with patterns during the breeding season in the wild. Our data indicate a potential uncoupling of the breeding physiology with the effect on DNA damage due to exposure to a resonance light cycle, which the birds may have interpreted as a skeleton photoperiod. Finally, though we were unable to fully disentangle the dynamics underlying seasonal DNA damage, we show that the previously documented patterns are not simply due to diel changes or the total amount of light exposure within a 24-hour period.

Biofabricated osteoblast-derived nanovesicles as extracellular vesicle mimics for bone repair

Osteoblast-derived extracellular vesicles (EVs) have demonstrated therapeutic utility for bone repair as transporters of key biomolecules capable of accelerating biomineralisation and tissue repair. The clinical translation of these biologically derived nanoparticles, however remains limited due to scalability, heterogeneity and standardisation issues. Herein we investigate the generation of nanovesicles (NVs) from mineralising osteoblasts by extrusion directly compared against natural EV counterparts from the same parental cells.Mineralising osteoblast-derived EVs (MO-EVs) were isolated via ultracentrifugation from cell culture media. The parental osteoblasts were then processed via serial extrusion to <200 nm. EVs and NVs were characterised by comparing their size, concentration and morphology. The presence of tetraspanin markers was detected by Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS). Osteoblasts viability and metabolic activity was assessed after both EV and NV-treatment before comparing their mineralising potency via alizarin red staining.EVs and NVs exhibited similar diameters of approximately 100 nm with a vesicular morphology. EVs were found to be richer in proteins and exhibited a significantly more negative ζ-potential compared to NVs. SP-IRIS analysis confirmed the presence of CD9, CD63 and CD81 in EVs. At both 1 and 10 μg/mL, EVs and NVs reduced the metabolic activity of osteoblasts, however, this was not associated with any cytotoxic effects. The biomineralisation study performed using osteoblasts showed that only EVs significantly increased mineral deposition (p < 0.05) compared to untreated control.In this study, we have established for the first time the biofabrication of cell-derived nanovesicles as a promising alternative to extracellular vesicles derived from mineralising osteoblasts.

Biosynthesis of novel non-proteinogenic amino acids β-hydroxyenduracididine and β-methylphenylalanine in Escherichia coli.

Non-proteinogenic amino acids (npAAs) are valuable building blocks for the development of advanced pharmaceuticals and agrochemicals. The surge in interest in their synthesis is primarily due to the potential to enhance and diversify existing bioactive molecules. This can be achieved by altering these bioactive molecules to improve their effectiveness, reducing resistance compared to their natural counterparts or generating molecules with novel functions. Traditional production of npAAs in native hosts requires specialized conditions and complex cultivation media. Furthermore, these compounds are often found in organisms that challenge genetic manipulation. Thus, the recombinant production of these npAAs in a model organism like Escherichia coli paves the way for groundbreaking advancements in synthetic biology. Two synthetic operons, comprising of five heterologous proteins were genomically integrated into E. coli for the synthesis of npAAs β-methylphenylalanine (BmePhe), β-hydroxyenduracididine (BhEnd), and enduracididine (End). Proteomic and metabolomic analysis confirmed production of these compounds in E. coli for the first time. Interestingly, we discovered that the exogenous addition of pathway precursors to the E. coli system enhanced the yield of BmePhe by 2.5 times, whereas it concurrently attenuated the production of BhEnd and End, signifying a selective precursor-dependent yield enhancement. The synthetic biology landscape is broadened in this study by expanding the repertoire of amino acids beyond the conventional set of 22 standard proteinogenic amino acids. The biosynthesized npAAs, End, BhEnd, and BmePhe hold promise for engineering proteins with modified functions, integrating into novel metabolites and/or enhancing biological stability and activity. Additionally, these amino acids' biological production and subsequent purification present an alternative to traditional chemical synthesis methods, paving a direct pathway for pharmacological evaluation.

Navigating directed evolution efficiently: optimizing selection conditions and selection output analysis.

Directed evolution is a powerful tool that can bypass gaps in our understanding of the sequence-function relationship of proteins and still isolate variants with desired activities, properties, and substrate specificities. The rise of directed evolution platforms for polymerase engineering has accelerated the isolation of xenobiotic nucleic acid (XNA) synthetases and reverse transcriptases capable of processing a wide array of unnatural XNAs which have numerous therapeutic and biotechnological applications. Still, the current generation of XNA polymerases functions with significantly lower efficiency than the natural counterparts and retains a significant level of DNA polymerase activity which limits their in vivo applications. Although directed evolution approaches are continuously being developed and implemented to improve XNA polymerase engineering, the field lacks an in-depth analysis of the effect of selection parameters, library construction biases and sampling biases. Focusing on the directed evolution pipeline for DNA and XNA polymerase engineering, this work sets out a method for understanding the impact of selection conditions on selection success and efficiency. We also explore the influence of selection conditions on fidelity at the population and individual mutant level. Additionally, we explore the sequencing coverage requirements in directed evolution experiments, which differ from genome assembly and other -omics approaches. This analysis allowed us to identify the sequencing coverage threshold for the accurate and precise identification of significantly enriched mutants. Overall, this study introduces a robust methodology for optimizing selection protocols, which effectively streamlines selection processes by employing small libraries and cost-effective NGS sequencing. It provides valuable insights into critical considerations, thereby enhancing the overall effectiveness and efficiency of directed evolution strategies applicable to enzymes other than the ones considered here.

Identification, Purification, and Characterization of Kunitz-Type Protease Inhibitors from White-Fleshed Dragon Fruit (Selenicereus undatus) and Red-Fleshed Dragon Fruit (Selenicereus costaricensis) Seeds as Novel Food Allergens.

There have been clinical reports of allergies to dragon fruits. However, little is known about the allergens that trigger these reactions. This study aimed to investigate novel allergens in dragon fruits. The peptide mass fingerprints of two purified natural allergens were identified by LC-MS/MS with chymotrypsin proteolysis. The complete amino acid sequences of the allergens were deduced from cDNA amplicon sequences. The coding sequences of two allergens were inserted in the expression vector pColdI, and recombinant allergens were produced in Escherichia coli. Circular dichroism was performed to analyze the secondary structures of natural and recombinant allergens. Our results identified two novel allergens as Kunitz-type protease inhibitors. Recombinant allergens exhibited well-folded structures, predominantly composed of β-sheets, similar to their natural counterparts. IgE reactivity analysis with sera from ten patients primarily sensitized to dragon fruit indicated that Kunitz-type protease inhibitors are major allergens in dragon fruits. These results improve our understanding of allergen sources and provide important insights into the allergenicity of proteins from different species.

Natural Dyes: A Comprehensive Review on Medicinal Plant-based Pigments and Culinary Herbs as Flavor Enhancers

The global demand for natural dyes has surged, propelled by a growing awareness of the therapeutic properties inherent in these dyes. Derived from a variety of sources such as plants, insects, animals, and minerals, natural dyes have garnered attention as safer alternatives to synthetic colorants, many of which have been banned due to their potential to cause allergy-like symptoms or pose carcinogenic risks. Notably, plant-based pigments among natural dyes exhibit a diverse array of medicinal values. This review provides an in-depth exploration of various types of dyes, highlighting the distinctions between natural and synthetic counterparts and delvloping into their wide-ranging applications. The adverse effects associated with synthetic dyes are discussed, emphasizing the need for sustainable alternatives. The paper also offers a compilation of information on synonyms, biological sources, chemical constituents, and uses found in naturally occurring dye-yielding plants, aiming to contribute to the development of pharmaceutical and cosmeceutical formulations. This comprehensive review amalgamates the realms of natural dyes and culinary herbs, offering valuable insights into their medicinal and culinary significance.

Analysis of in-bin low-temperature and high-temperature grain drying in Alberta: Specific energy, carbon costs and policy implications

Optimizing grain drying process is pivotal for both economic viability and environmental sustainability. In cold countries, supplemental heating is paramount but instigates the issue of carbon release at the same time. To curve the emission, a carbon levy has been imposed that varies with fuel types. However, there is limited knowledge of the impact of field-adaptable technologies utilizing commercialized fuels on the optimal execution of grain drying. To explore this, a comprehensive three-year on-farm grain drying study was conducted in the province of Alberta, Canada. This comparative analysis centered on three critical aspects, i.e., specific energy consumption, greenhouse gas emissions (GHGs), and operating costs. Furthermore, the research extended its projections into the year 2030, accounting for the impact of gradual carbon levies on natural gas, propane, and diesel fuel systems. Resultsshowed that indirect heaters in in-bin systems were 38 % more energy-efficient than direct heaters due to better airflow and higher initial grain temperatures, while indirect heaters with diesel burners exhibited 27.8 % lower burner turndown ratios and 35.4 % higher energy consumption than natural gas counterparts. In high-temperature drying, natural gas consumption decreased as supply air temperatures rose, with double-flow dryer showing the lowest energy consumption (6.3±1.9 GJ/t) in comparison to mixed-flow and cross-flow dryer due to waste heat recovery. Heaters and Dryers operated at varying load capacities, indicated 126–135 % increase in natural gas cost with carbon levy by 2030. Achieving lower specific energy consumption in grain drying requires precise burner and process control, along with maintenance, offering valuable guidance for producers.

Highly Selective Artificial K+ Transporters Reverse Liver Fibrosis In Vivo.

Liver fibrosis is a life-threatening disease that currently lacks clinically effective therapeutic agents. Given the close correlation between dysregulated intracellular K+ homeostasis and the progression of liver fibrosis, developing artificial K+ transporters mimicking the essential function of their natural counterparts in regulating intracellular K+ levels might offer an appealing yet unexplored treatment strategy. Here, we present an unconventional class of artificial K+ transporters involving the "motional" collaboration between two K+ transporter molecules. In particular, 6C6 exhibits an impressive EC50 value of 0.28 μM (i.e., 0.28 mol % relative to lipid) toward K+ and an exceptionally high K+/Na+ selectivity of 15.5, representing one of the most selective artificial K+ transporters reported to date. Most importantly, our study demonstrates, for the first time, the potential therapeutic effect of K+-selective artificial ion transporters in reversing liver fibrosis both in vitro and in vivo.

Synthesis, biological activities and mechanistic studies of C20-ketone pachysandra alkaloids as anti-hepatocellular carcinoma agents.

The pachysandra alkaloids found in Sarcococca ruscifolia demonstrate notable anti-hepatocellular carcinoma activity. Despite their efficacy, the structural diversity of these compounds remains limited, and their precise antitumor mechanism is still unclear. In pursuit of identifying novel lead compounds with high efficacy and low toxicity for combating hepatocellular carcinoma, twenty-three compounds of C20-ketone pachysandra alkaloid derivatives were designed and synthesized by using 3-dimethylamine pachysandra alkaloids as scaffolds. Subsequent in vitro anticancer activity experiments showed that synthetic pachysandra alkaloids had a stronger effect on HepG2 cells than did their natural counterparts, with low toxicity and high selectivity. The most potent derivative, 6k, had an IC50 value of 0.75μM, demonstrating 25.7-fold greater anticancer activity than sarcovagine D against HepG2 cells. Through network pharmacology and molecular docking analysis, it was revealed that synthetic pachysandra alkaloids may exert their effects by inhibiting the JAK2/STAT3 pathway, thereby preventing the proliferation of liver cancer cells. Further research through scratch tests, immunofluorescence experiments, and Western blot analysis revealed that compound 6k effectively inhibited the migration of HepG2 cells and induced mitochondria-mediated intrinsic apoptosis of HepG2 cells by regulating the JAK2/STAT3 signaling pathway. The aforementioned results indicate that compound 6k could be developed as a potential candidate for the treatment of hepatocellular carcinoma.

Material engineering and application of hybrid biomimetic-de novo designed elastin-like polypeptides

The global concern over environmental consequences of petrochemical-derived plastics underscores the urgent need for sustainable and biodegradable polymers. In this context, elastin-like polypeptides emerge as a promising solution, offering multiple advantages, including remarkable mechanical properties, biocompatibility, customizable functionalities, and renewable sourcing through biosynthetic production in microbes, making them a compelling choice for various applications. We previously demonstrated accelerated engineering of a new class of elastin-like polypeptide‐based materials through hybrid biomimetic‐de novo predictive molecular design. The resulting variants exhibited enhanced molecular stability compared to their natural counterparts, catering to a range of technical applications that involve harsh downstream processing conditions. Here, we showcase the use of some of these previously discovered hybrid variants and illustrate the effective translation of the predicted molecular designs in structural and functional materials in several high-added-value applications. This includes multiscale drug-encapsulating vehicles with controlled release, multifunctional wound coverings, and all-aqueous-based biobased photoresists for creating 2D/3D microstructures.

Medical Image Classification with a Hybrid SSM Model Based on CNN and Transformer

Medical image classification, a pivotal task for diagnostic accuracy, poses unique challenges due to the intricate and variable nature of medical images compared to their natural counterparts. While Convolutional Neural Networks (CNNs) and Transformers are prevalent in this domain, each architecture has its drawbacks. CNNs, despite their strength in local feature extraction, fall short in capturing global context, whereas Transformers excel at global information but can overlook fine-grained details. The integration of CNNs and Transformers in a hybrid model aims to bridge this gap by enabling simultaneous local and global feature extraction. However, this approach remains constrained in its capacity to model long-range dependencies, thereby hindering the efficient extraction of distant features. To address these issues, we introduce the MambaConvT model, which employs a state-space approach. It begins by locally processing input features through multi-core convolution, enhancing the extraction of deep, discriminative local details. Next, depth-separable convolution with a 2D selective scanning module (SS2D) is employed to maintain a global receptive field and establish long-distance connections, capturing the fine-grained features. The model then combines hybrid features for comprehensive feature extraction, followed by global feature modeling to emphasize on global detail information and optimize feature representation. This paper conducts thorough performance experiments on different algorithms across four publicly available datasets and two private datasets. The results demonstrate that MambaConvT outperforms the latest classification algorithms in terms of accuracy, precision, recall, F1 score, and AUC value ratings, achieving superior performance in the precise classification of medical images.

Metagenomic insights into ecological risk of antibiotic resistome and mobilome in riverine plastisphere under impact of urbanization

Microplastics (MPs) are of increasing concern due to their role as reservoirs for antibiotic resistance genes (ARGs) and pathogens. To date, few studies have explored the influence of anthropogenic activities on ARGs and mobile genetic elements (MGEs) within various riverine MPs, in comparison to their natural counterparts. Here an in-situ incubation was conducted along heavily anthropogenically-impacted Houxi River to characterize the geographical pattern of antibiotic resistome, mobilome and pathogens inhabiting MPs- and leaf-biofilms. The metagenomics result showed a clear urbanization-driven profile in the distribution of ARGs, MGEs and pathogens, with their abundances sharply increasing 4.77 to 19.90 times from sparsely to densely populated regions. The significant correlation between human fecal marker crAssphage and ARG (R2 = 0.67, P=0.003) indicated the influence of anthropogenic activity on ARG proliferation in plastisphere and natural leaf surfaces. And mantel tests and random forest analysis revealed the impact of 17 socio-environmental factors, e.g., population density, antibiotic concentrations, and pore volume of materials, on the dissemination of ARGs. Partial least squares-path modeling further unveiled that intensifying human activities not only directly boosted ARGs abundance but also exerted a comparable indirect impact on ARGs propagation. Furthermore, the polyvinylchloride plastisphere created a pathogen-friendly habitat, harboring higher abundances of ARGs and MGEs, while polylactic acid are not likely to serve as vectors for pathogens in river, with a lower resistome risk score than that in leaf-biofilms. This study highlights the diverse ecological risks associated with the dissemination of ARGs and pathogens in varied MPs, offering insights for the policymaking of usage and control of plastics within urbanization.

Biotechnological Production of the Recombinant Two-Component Lantibiotic Lichenicidin in a Bacterial Expression System

Objective: Lantibiotics are a family of bacterial antimicrobial peptides synthesized by ribosomes, that undergo post-translational modification to form lanthionine (Lan) and methyllanthionine (MeLan) residues. Lantibiotics are currently considered promising agents for combating antibiotic-resistant bacterial infections. This paper presents a biotechnological method for obtaining two components of the lantibiotic lichenicidin from Bacillus licheniformis B-511, Lchα and Lchβ. Such a system has the potential to facilitate the production of not only lichenicidin, but also other lantibiotics, including two-component ones, and also to enable the study of their biosynthesis and the activity and substrate specificity of modifying enzymes. Methods: The developed system is based on heterologous coexpression of the genes of Lchα and Lchβ precursors with the genes of their corresponding modifying enzymes in the cytoplasm of Escherichia coli BL21(DE3). Subsequent steps included immobilized metal affinity chromatography of the His-tagged hybrid peptide under denaturing conditions, cyanogen bromide cleavage in acidic medium, and final purification using reverse-phase HPLC. Results and Discussion: The system was employed for the expression and purification of lantibiotics, resulting in the successful isolation of the β-component of lichenicidin in high yield (approximately 4 mg/L of culture). This purified beta component exhibited structural and functional characteristics comparable to its natural counterpart, which was purified from the natural producer. However, the yield of the mature α-component of lichenicidin in such a system was significantly lower. Conclusions: The work presents a biotechnological method for obtaining recombinant two-component lantibiotic lichenicidin, which has proven to be particularly effective in the case of Lchβ. The developed method can also be applied to the production of other promising lantibiotics and their further research.

A new concept of semistrict quasiconvexity for vector functions

We establish a new concept of semistrict quasiconvexity for vector functions defined on a nonempty convex set in a real linear space X that take values in some real topological linear space Y, partially ordered by a proper solid convex cone C. The so-called semistrict C-quasiconvexity notion recovers the classical concept of semistrict quasiconvexity of scalar functions when Y = R and C = R + . Additionally, analogous to the scalar scenario, if the cone C is closed, a vector function is both semistrictly C-quasiconvex and C-quasiconvex (in the sense of Luc, 1989) if and only if it is explicitly C-quasiconvex (in the sense of Popovici, 2007). Finally, we convey a characterization of semistrictly C-quasiconvex functions by means of scalar semistrictly quasiconvex functions that are compositions of the nonlinear scalarization functions introduced by Gerstewitz (Tammer) in 1983 with the initial vector function. In light of this characterization, the new concept of semistrict C-quasiconvexity seems to be a natural vector counterpart for the scalar concept of semistrict quasiconvexity.

Robot dolphin can swim, hover, and walk like its natural counterparts

In simulations, dolphin-inspired autonomous underwater vehicle can mimic dolphin’s ability to remain upright at the water surface.

Molybdomenite-P21/c, Polymorphous with Molybdomenite and the Natural Analogue of Synthetic α-PbSe4+O3, from the El Dragón Mine, Potosí, Bolivia

Abstract A polymorph of PbSe4+O3, designated as molybdomenite-P21/c, has been discovered from the El Dragón mine, Potosí Department, Bolivia. It occurs as thin-bladed crystals. Associated minerals are Co-bearing krut’aite–penroseite, chalcomenite, and dolomite. Molybdomenite- P21/c is pale yellow in transmitted light and has a greasy luster. It is brittle and has a Mohs hardness of 3. No cleavage was observed. The calculated density is 7.034 g/cm3. An electron microprobe analysis yielded an empirical formula (based on 3 O apfu) of Pb1.00Se1.00O3. Molybdomenite-P21/c is the natural counterpart of synthetic α-PbSe4+O3, which is dimorphous with grandfathered P21/m molybdomenite (or β-PbSe4+O3). It is monoclinic with space group P21/c and unit-cell parameters a = 9.154(8), b = 8.071(6), c = 8.780(7) Å, β = 103.15(8) °, and V = 631.6(6) Å3. The crystal structure of molybdomenite-P21/c consists of two symmetrically distinct Pb (Pb1 and Pb2), two Se (Se1 an Se2), and six O atoms. Each Se4+ cation is bonded to three O atoms, forming a typical (Se4+O3)2− trigonal pyramid. Both Pb1 and Pb2 atoms are coordinated by nine O atoms. Each [PbO9] polyhedron is linked to six (SeO3)2− pyramids, three by sharing edges and three by sharing corners. The [PbO9] polyhedra are connected to one another through sharing edges and by (SeO3)2− groups, giving rise to a complex three-dimensional net system. Topologically, the crystal structure of molybdomenite-P21/c is identical to that of molybdomenite. Raman spectroscopic measurements reveal that there is only one strong peak centered at 790 cm−1, attributable to the Se4+–O symmetric stretching vibrations within the (SeO3)2− groups, for molybdomenite, whereas there are two such strong peaks, one at 788 cm−1 and the other at 804 cm−1, for molybdomenite-P21/c.