Superposition Of Structures Research Articles

The Characterization of the Lower Town of the UNESCO Archaeological Site of Arslantepe (Malatya, Türkiye) Using the Geophysical E-PERTI Method (Extended Data-Adaptive Probability-Based Electrical Resistivity Tomography Inversion Method)

The UNESCO site of Arslantepe is located in Eastern Anatolia in the Malatya Plain (Türkiye) about 10 km from the Euphrates River. Here for about a century archaeological excavations have been carried out, reconstructing a long sequence of human frequentation starting from 5000 years BC up to the Middle Ages. The settlement, one of the most important and largest in the region, has undergone numerous changes over time, resulting in a complex superposition of structures, palaces, temples, and burials concentrated on the hill. With the aim of extending the knowledge of the site, in 2022, geophysical surveys were carried out through the application of electrical resistivity tomography, covering a surface of approximately 4300 m2 in an unexplored area at the foot of the hill. In this paper, the Extended data-adaptive Probability-based Electrical Resistivity Tomography Inversion approach (E-PERTI), recently published as a development of the probability tomography imaging approach, has been applied to a large apparent resistivity field dataset, providing the best estimate of the most probable estimate of the resistivity distribution through an intrinsic linear regression model implementing standard least squares routines. The results seem to prove the effectiveness of the E-PERTI approach in noise dejection, enhancing associated resistivity highs that can be ascribable to the trace of a potential fortification. The obtained information represents new, unexpected data that open new frontiers of archaeological research, adding value to the knowledge of the site.

Small angle X-ray scattering and in silico based structure and function analysis of a novel xylobiohydrolase (AcGH30A) from Acetivibrio clariflavus

Xylobiohydrolase plays a crucial role in the hydrolysis of xylan, a complex polysaccharide present in the cell walls of plants. This study focuses on the solution structure and substrate binding analysis of a novel xylobiohydrolase, AcGH30A, from Acetivibrio clariflavus. Secondary structure analysis of AcGH30A in an aqueous environment using Circular Dichroism and in silico modeling revealed an α/β/α sandwich structure with a central β-barrel comprising eight β-strands. Superposition of the homology-modelled structure of AcGH30A with its closest homolog showed that the active-site contains Glu175 and Glu268 as the catalytic residues. Molecular docking confirmed xylobiose as the preferred ligand, showcasing polar interactions with the catalytic amino acids, indicating its xylobiohydrolase activity. AcGH30A displayed a high binding affinity with xylobiose with an association constant (Ka ) of 7.83 × 105 M−1, as determined by isothermal titration calorimetry. Molecular dynamics (MD) simulations of AcGH30A and AcGH30A-xylobiose complex in solution showed reduced RMSD, Rg and SASA values, confirming the stability and compactness of the complex. MD simulations further highlighted the crucial role of Glu175 in hydrogen bonding with the ligand, which acts as an acid or base. Small-angle X-ray scattering (SAXS) analysis of AcGH30A showed its molecular shape as an earbud with a globular structure existing in a monodispersed state, which was corroborated by dynamic light scattering (DLS). The hydrodynamic radius (Rh ) of AcGH30A, determined by DLS, was 3.7 nm. This study significantly contributed valuable insights into the structure and functional aspects of AcGH30A.

ARTEMIS: a method for topology-independent superposition of RNA 3D structures and structure-based sequence alignment.

Non-coding RNAs play a major role in diverse processes in living cells with their sequence and spatial structure serving as the principal determinants of their function. Superposition of RNA 3D structures is the most accurate method for comparative analysis of RNA molecules and for inferring structure-based sequence alignments. Topology-independent superposition is particularly relevant, as evidenced by structurally similar RNAs with sequence permutations such as tRNA and Y RNA. To date, state-of-the-art methods for RNA 3D structure superposition rely on intricate heuristics, and the potential for topology-independent superposition has not been exhausted. Recently, we introduced the ARTEM method for unrestrained pairwise superposition of RNA 3D modules and now we developed it further to solve the global RNA 3D structure alignment problem. Our new tool ARTEMIS significantly outperforms state-of-the-art tools in both sequentially-ordered and topology-independent RNA 3D structure superposition. Using ARTEMIS we discovered a helical packing motif to be preserved within different backbone topology contexts across various non-coding RNAs, including multiple ribozymes and riboswitches. We anticipate that ARTEMIS will be essential for elucidating the landscape of RNA 3D folds and motifs featuring sequence permutations that thus far remained unexplored due to limitations in previous computational approaches.

Vector synthesis of fault testing map for logic

Vector synthesis of fault testing (simulation) map for logic is proposed, which without simulation allows to determine of all faults detected on test sets, as well as determining test sets to detect specified faults. For synthesis, a superposition of smart data structures is used, containing: a deductive matrix D, as a derivative of the logical vector L, test truth table T, and fault truth table F. The deductive matrix is seen as the gene of functionality and base of fault simulation mechanism to solve all the problems of testing and verification. In the matrix synthesis, an axiom is used: all the mentioned tables are identical in shape to each other and always interact with each other convolutionally T⊕L⊕F=0. A universal deductive reversing converter “test-faults” and “faults-test” for logical functionalities of any dimension is proposed. Converter functions: fault simulation on test sets T→F and synthesis of test sets F→T to detect the specified faults. The converter can be used as a test generation and fault simulation service for IP-core system-on-chip (SoC) under the IEEE 1500 SECT standard. Based on the deductive matrix, a fault testing map for logic is built, where each test set is matched with the logic-detected faults of the input lines.

GTalign: spatial index-driven protein structure alignment, superposition, and search

With protein databases growing rapidly due to advances in structural and computational biology, the ability to accurately align and rapidly search protein structures has become essential for biological research. In response to the challenge posed by vast protein structure repositories, GTalign offers an innovative solution to protein structure alignment and search—an algorithm that achieves optimal superposition at high speeds. Through the design and implementation of spatial structure indexing, GTalign parallelizes all stages of superposition search across residues and protein structure pairs, yielding rapid identification of optimal superpositions. Rigorous evaluation across diverse datasets reveals GTalign as the most accurate among structure aligners while presenting orders of magnitude in speedup at state-of-the-art accuracy. GTalign’s high speed and accuracy make it useful for numerous applications, including functional inference, evolutionary analyses, protein design, and drug discovery, contributing to advancing understanding of protein structure and function.

Mineral Exploration of the Former Province of Kasaï-Occidental through the Analysis of Land and Satellite Gravity Data

This paper is based on the application of terrestrial and satellite gravimetry in mining and petroleum research in the former province of Kasai- Occidental in the Democratic Republic of Congo. This former province was split into two new provinces: Kasaï and Kasaï-Central. From a geological point of view, this area is dominated by Mesozoic and Cenozoic rocks in its northern part and by Precambrian rocks very rich in minerals in its southern part. Due to the insufficiency of terrestrial gravity data from pre-existing campaigns, we had access to satellite data from the International Gravimetric Bureau platform in order to have better resolution in the mapping of the subsurface of this region. The data processing methodology consisted of background noise attenuation as well as regional-residual separation. The gravity sets detected on the Bouguer anomaly map were grouped into high and low intensity zones. The structural map on which we have traced the faults and fold axes shows a preferential orientation of these structures in the NW-SE direction. The superposition of mineral occurrences and geological structures highlighted allowed us to split this zone into two parts: The southern part whose gravity highs concentrate the majority of diamond and iron occurrences and the gravity depressions which concentrate the indices of Lead, Nickel, Manganese; as well as the northern part located in the center of the Central Cuvette which contains a great thickness of sediments constituting, therefore, a favorable place for the maturation of the source rocks.

Unveiling the Interlayer Interaction in a 1H/1T TaS2 van der Waals Heterostructure.

This study delves into the intriguing properties of the 1H/1T-TaS2 van der Waals heterostructure, focusing on the transparency of the 1H layer to the charge density wave of the underlying 1T layer. Despite the sizable interlayer separation and metallic nature of the 1H layer, positive bias voltages result in a pronounced superposition of the 1T charge density wave structure on the 1H layer. The conventional explanation relying on tunneling effects proves insufficient. Through a comprehensive investigation combining low-temperature scanning tunneling microscopy, scanning tunneling spectroscopy, non-contact atomic force microscopy, and first-principles calculations, we propose an alternative interpretation. The transparency effect arises from a weak yet substantial electronic coupling between the 1H and 1T layers, challenging prior understanding of the system. Our results highlight the critical role played by interlayer electronic interactions in van der Waals heterostructures to determine the final ground states of the systems.

Unraveling deformation mechanism of the Fukang fold-and-thrust belt: Insight into intracontinental orogenesis of the Bogda Mountain, NW China

Characterized by the superposition of well-developed thick-skinned and thin-skinned structures, the Fukang fold-and-thrust belt is an ideal place for understanding the intracontinental orogenic process of the Bogda Mountain in the Tianshan orogenic belt, China. This study comprehensively examines the geological architecture, structural evolution, and deformation mechanism of the Fukang fold-and-thrust belt using high-resolution seismic reflection data, apatite-fission track analysis, and discrete element simulation. Seismic profile reveals that the Fukang fold-and-thrust belt exhibits superimposed tectonic styles, including a thrust duplex involving Carboniferous strata and an overlapping thrust imbricate structure. Stratigraphic unconformities and thermochronological results from apatite fission track suggest that this belt experienced five main episodes of compressional deformation in the Late Permian, Middle-Late Triassic, Middle-Late Jurassic, Late Cretaceous-Paleocene, and Late Miocene-present. The discrete element simulation results indicate that the Late Permian initial compressional deformation was triggered by reactivation of the pre-existing extensional faults. Subsequent episodic deformation was primarily controlled by thrusting along the Upper Carboniferous and Middle Permian decollement layers. This study highlights the predominant roles of the pre-existing faults and the decollement layers in the formation and evolution of the piedmont fold-and-thrust belt of the Bogda Mountain at distinct stages, serving as critical factors in determining the extent and amplitude of an intracontinental orogenic belt.

Theoretical insight on structure, electronic, and optical properties of two d 0–d 10 electron transition-metal oxyhalides SHG materials

Materials containing mixed anions, particularly, oxyhalides containing asymmetric functional building units, may lead to the discovery of excellent nonlinear optical (NLO) materials. In the present work, the geometric structure, mechanical properties, electronic structure and optical properties of two d 0–d 10 electron transition-metal oxyhalides Cs2CdV2O6Cl2 and Cs3CdV4O12Br have been systematically determined based on density functional theory. The asymmetric functional building units [V2O7], [V4O13], [CdO2Cl4] and [CdO4Br2] exhibit varying degrees of second-order Jahn−Teller distortions, contributing differently to the macroscopic nonlinearity. Mechanical properties reveal that the two oxyhalides are structurally and mechanically stable. Detailed electronic and optical properties of the two oxyhalides are provided. Optical anisotropy character is exhibited along different polarization vectors, giving a large birefringence for satisfying the phase-matching condition. Maximum absolute values of static second harmonic generation (SHG) coefficients are 4.47 pm V−1 for Cs2CdV2O6Cl2 and 3.72 pm V−1 for Cs3CdV4O12Br, suggesting that Cs2CdV2O6Cl2 and Cs3CdV4O12Br are potential NLO crystals with large SHG coefficients. In particular, unique 3D framework structures give a polar structure superposition of individual moments for asymmetric functional building units. Thus, maximum magnitudes of the total microscopic dipole are achieved, having the largest influence on the SHG response. This study elucidates the relationship between the structure and properties of transition-metal oxyhalides, providing valuable insights for designing NLO materials with excellent performance.

AlphaFind: discover structure similarity across the proteome in AlphaFold DB.

AlphaFind is a web-based search engine that provides fast structure-based retrieval in the entire set of AlphaFold DB structures. Unlike other protein processing tools, AlphaFind is focused entirely on tertiary structure, automatically extracting the main 3D features of each protein chain and using a machine learning model to find the most similar structures. This indexing approach and the 3D feature extraction method used by AlphaFind have both demonstrated remarkable scalability to large datasets as well as to large protein structures. The web application itself has been designed with a focus on clarity and ease of use. The searcher accepts any valid UniProt ID, Protein Data Bank ID or gene symbol as input, and returns a set of similar protein chains from AlphaFold DB, including various similarity metrics between the query and each of the retrieved results. In addition to the main search functionality, the application provides 3D visualizations of protein structure superpositions in order to allow researchers to instantly analyze the structural similarity of the retrieved results. The AlphaFind web application is available online for free and without any registration at https://alphafind.fi.muni.cz.

A study of multi-acoustic black holes considering suitability of attachment positions for suppressing low-frequency vibrations on large motor

Vibrations generated from machinery in various industries, such as the automotive, aerospace, and shipbuilding industries, must be suppressed for developing low-vibration and low-noise systems. High-frequency vibrations can be easily controlled via damping treatments; however, controlling vibrations in the low-frequency range generated from large machinery is a major challenge. In general, a substantial amount of damping material is required for suppressing low-frequency vibrations. This is unsuitable when developing low-cost, lightweight, and eco-friendly systems. To overcome the limitations, effective methods are required for suppressing these low-frequency vibrations. In this study, an effective method was proposed for suppressing vibrations in the low-frequency range using multiple acoustic black holes (multi-ABHs) considering the suitability values of the attachment positions, which were determined by flexural wave propagation and interactions between the multi-ABHs and structures. The suitability values of the attachment positions are proposed as non-dimensional parameters that are calculated using the structural intensity and mode superposition methods. For validating the proposed method, the vibration suppression characteristics were analyzed using a steel plate. The analyzed cases were categorized into six groups according to the suitability values of the attachment positions of the multi-ABHs. The largest reduction in vibrations was observed when the multi-ABHs were attached to the location with the highest suitability in the six cases. Finally, the multi-ABHs were applied to a large 2-pole motor considering the suitability values of the attachment positions, and the dominant vibrations at 60, 120, and 180 Hz frequencies were suppressed.

An AlphaFold Structure Analysis of COQ2 as Key a Component of the Coenzyme Q Synthesis Complex.

Coenzyme Q (CoQ) is a lipidic compound that is widely distributed in nature, with crucial functions in metabolism, protection against oxidative damage and ferroptosis and other processes. CoQ biosynthesis is a conserved and complex pathway involving several proteins. COQ2 is a member of the UbiA family of transmembrane prenyltransferases that catalyzes the condensation of the head and tail precursors of CoQ, which is a key step in the process, because its product is the first intermediate that will be modified in the head by the next components of the synthesis process. Mutations in this protein have been linked to primary CoQ deficiency in humans, a rare disease predominantly affecting organs with a high energy demand. The reaction catalyzed by COQ2 and its mechanism are still unknown. Here, we aimed at clarifying the COQ2 reaction by exploring possible substrate binding sites using a strategy based on homology, comprising the identification of available ligand-bound homologs with solved structures in the Protein Data Bank (PDB) and their subsequent structural superposition in the AlphaFold predicted model for COQ2. The results highlight some residues located on the central cavity or the matrix loops that may be involved in substrate interaction, some of which are mutated in primary CoQ deficiency patients. Furthermore, we analyze the structural modifications introduced by the pathogenic mutations found in humans. These findings shed new light on the understanding of COQ2's function and, thus, CoQ's biosynthesis and the pathogenicity of primary CoQ deficiency.

Remarkable energy-storage density together with efficiency of above 92% in high-entropy ferroelectric ceramics

Recently, the use of “entropy engineering” to form high-entropy ceramic dielectric materials is considered to be an effective means to break through the traditional doping which modified local structures. However, the low energy storage efficiency (η) of most high-entropy ceramics cannot match their excellent energy storage density (Wrec). This work is the first to combine scheelite structure (SmTaO4) with high-entropy perovskite structure ((NaBiBaSrCa)0.2TiO3). On the one hand, the superposition of multiple structures makes the inherent lattice distortion and sluggish diffusion of high-entropy materials more obvious, thus playing a role in refining grains, reducing leakage current density, and obtaining a high breakdown electric field (Eb). On the other hand, the introduction of donor elements inhibits the generation and migration of oxygen vacancies, reducing losses to improve η and Eb. Ultimately, the goal of obtaining a remarkable Wrec (5.6 J/cm3) and η (92.2%) at 445 kV/cm was successfully achieved. This work offers a practical approach to attain superior overall performances in high-entropy ceramics.

PELE scores: pelvic X-ray landmark detection with pelvis extraction and enhancement.

Pelvic X-ray (PXR) is widely utilized in clinical decision-making associated with the pelvis, the lower part of the trunk that supports and balances the trunk. In particular, PXR-based landmark detection facilitates downstream analysis and computer-assisted diagnosis and treatment of pelvic diseases. Although PXR has the advantages of low radiation and reduced cost compared to computed tomography (CT), it characterizes the 2D pelvis-tissue superposition of 3D structures, which may affect the accuracy of landmark detection in some cases. However, the superposition nature of PXR is implicitly handled by existing deep learning-based landmark detection methods, which mainly design the deep network structures for better detection performances. Explicit handling of the superposition nature of PXR is rarely done. In this paper, we explicitly focus on the superposition of X-ray images. Specifically, we propose a pelvis extraction (PELE) module that consists of a decomposition network, a domain adaptation network, and an enhancement module, which utilizes 3D prior anatomical knowledge in CT to guide and well isolate the pelvis from PXR, thereby eliminating the influence of soft tissue for landmark detection. The extracted pelvis image, after enhancement, is then used for landmark detection. We conduct an extensive evaluation based on two public and one private dataset, totaling 850 PXRs. The experimental results show that the proposed PELE module significantly improves the accuracy of PXRs landmark detection and achieves state-of-the-art performances in several benchmark metrics. The design of PELE module can improve the accuracy of different pelvic landmark detection baselines, which we believe is obviously conducive to the positioning and inspection of clinical landmarks and critical structures, thus better serving downstream tasks. Our project has been open-sourced at https://github.com/ECNUACRush/PELEscores .

SiteMine: Large-scale binding site similarity searching in protein structure databases.

Drug discovery and design challenges, such as drug repurposing, analyzing protein-ligand and protein-protein complexes, ligand promiscuity studies, or function prediction, can be addressed by protein binding site similarity analysis. Although numerous tools exist, they all have individual strengths and drawbacks with regard to run time, provision of structure superpositions, and applicability to diverse application domains. Here, we introduce SiteMine, an all-in-one database-driven, alignment-providing binding site similarity search tool to tackle the most pressing challenges of binding site comparison. The performance of SiteMine is evaluated on the ProSPECCTs benchmark, showing a promising performance on most of the data sets. The method performs convincingly regarding all quality criteria for reliable binding site comparison, offering a novel state-of-the-art approach for structure-based molecular design based on binding site comparisons. In a SiteMine showcase, we discuss the high structural similarity between cathepsin L and calpain 1 binding sites and give an outlook on the impact of this finding on structure-based drug design. SiteMine is available at https://uhh.de/naomi.

Twistronics in two-dimensional transition metal dichalcogenide (TMD)-based van der Waals interface.

Transition metal dichalcogenides (TMD) based heterostructures have gained significant attention lately because of their distinct physical properties and potential uses in electronics and optoelectronics. In the present work, the effects of twist on the structural, electronic, and optical properties (such as the static dielectric constant, refractive index, extinction coefficient, and absorption coefficient) of vertically stacked TMD heterostructures, namely MoSe2/WSe2, WS2/WSe2, MoSe2/WS2 and MoS2/WSe2, have been systematically studied and a thorough comparison is done among these heterostructures. In addition, the absence of negative frequency in the phonon dispersion curve and a low formation energy confirm the structural and thermodynamical stability of all the proposed TMD heterostructures. The calculations are performed using first-principles-based density functional theory (DFT) method. Beautiful Moiré patterns are formed due to the relative rotation of the layers as a consequence of the superposition of the periodic structures of the TMDs on each other. Twist engineering allows the modulation of bandgaps and a phase change from direct to indirect band gap semiconductors as well. The high optical absorption in the visible range of spectrum makes these twisted heterostructures very promising candidates in photovoltaic applications.

Molecular mechanism of human ISG20L2 for the ITS1 cleavage in the processing of 18S precursor ribosomal RNA.

The exonuclease ISG20L2 has been initially characterized for its role in the mammalian 5.8S rRNA 3' end maturation, specifically in the cleavage of ITS2 of 12S precursor ribosomal RNA (pre-rRNA). Here, we show that human ISG20L2 is also involved in 18S pre-rRNA maturation through removing the ITS1 region, and contributes to ribosomal biogenesis and cell proliferation. Furthermore, we determined the crystal structure of the ISG20L2 nuclease domain at 2.9 Å resolution. It exhibits the typical αβα fold of the DEDD 3'-5' exonuclease with a catalytic pocket located in the hollow near the center. The catalytic residues Asp183, Glu185, Asp267, His322 and Asp327 constitute the DEDDh motif in ISG20L2. The active pocket represents conformational flexibility in the absence of an RNA substrate. Using structural superposition and mutagenesis assay, we mapped RNA substrate binding residues in ISG20L2. Finally, cellular assays revealed that ISG20L2 is aberrantly up-regulated in colon adenocarcinoma and promotes colon cancer cell proliferation through regulating ribosome biogenesis. Together, these results reveal that ISG20L2 is a new enzymatic member for 18S pre-rRNA maturation, provide insights into the mechanism of ISG20L2 underlying pre-rRNA processing, and suggest that ISG20L2 is a potential therapeutic target for colon adenocarcinoma.

Influence of nappe structure on the Carboniferous volcanic reservoir in the middle of the Hongche Fault Zone, Junggar Basin, China

Abstract This work presents an in-depth examination of the Carboniferous volcanic reservoir within the CH471 well area, situated in the central portion of the Hongche fault zone on the northwestern margin of the Junggar Basin. Leveraging seismic data and well connection comparisons, we scrutinize the tectonic evolution model and elucidate the impact of the nappe structure of the Hongche fault zone on the volcanic reservoir. The study has obtained the following understanding: after the formation of Carboniferous volcanic rocks, affected by the Hongche fault structure, a series of structural superpositions from extension to extrusion and finally thrust occurred, resulting in a northwestward tilt of the volcanic rock mass, and a large number of cracks were generated inside the rock mass. At the same time, the top was uplifted and affected by weathering and leaching to form a weathering crust, eventually forming a reservoir. The northern part is located in the edge area of the eruption center, and the rock mass has good stratification. The rock strata have certain constraints on the reservoir distribution, and the reservoir is inclined along the rock mass. The southern part is close to the eruption center and features large volcanic breccia accumulation bodies with strong internal heterogeneity. The reservoir developed mainly in the superposition of the range of control of the weathering crust and dense fracture development, and the rock mass morphology does not control the area. Structure is the key to forming a volcanic rock reservoir, mainly reflected in the following aspects. First, tectonic activity is accompanied by fracture development, and fractures are densely developed in areas with strong activity, which can effectively improve the physical properties of volcanic reservoirs. Second, tectonic activity leads to the strata uplift and weathering denudation, forming a weathering crust. Within the range of control of weathering and leaching, the physical properties of volcanic rocks are improved, and it is easier to form high-quality reservoirs. Third, the distribution of volcanic rock masses is controlled by tectonic activity, which affects the reservoir controlled by the dominant lithology.

Volumetric and Simultaneous Photoacoustic and Ultrasound Imaging with a Conventional Linear Array in a Multiview Scanning Scheme.

Volumetric, multimodal imaging with precise spatial and temporal co-registration can provide valuable and complementary information for diagnosis and monitoring. Considerable research has sought to combine 3D photoacoustic (PA) and ultrasound (US) imaging in clinically translatable configurations. However, technical compromises currently result in poor image quality either for photoacoustic or ultrasonic modes. This work aims to provide translatable, high quality, simultaneously co-registered dual-mode PA/US 3D tomography. Volumetric imaging based on a synthetic aperture approach was implemented by interlacing PA and US acquisitions during a rotate-translate scan with a 5-MHz linear array (12 angles and 30-mm translation to image a 21-mm diameter, 19 mm long cylindrical volume within 21 seconds). For co-registration, an original calibration method using a specifically designed thread phantom was developed to estimate 6 geometrical parameters and 1 temporal off-set through global optimization of the reconstructed sharpness and superposition of calibration phantom structures. Phantom design and cost function metrics were selected based on analysis of a numerical phantom, and resulted in a high estimation accuracy for the 7 parameters. Experimental estimations validated the calibration repeatability. The estimated parameters were used for bimodal reconstruction of additional phantoms with either identical or distinct spatial distributions of US and PA contrasts. Superposition distance of the two modes was within < 10% of the acoustic wavelength and a wavelength-order uniform spatial resolution was obtained. This dual-mode PA/US tomography should contribute to more sensitive and robust detection and follow-up of biological changes or the monitoring slower-kinetic phenomena in living systems such as the accumulation of nanoagents.

Effect of chromium substitution on structural and optical properties of Ca3(VO4)2 for laser and SRS applications

Crystal structures of Czochralski-grown Ca3(VO4)2 single crystals doped with over-stoichiometric 0.01, 0.05, and 0.1 wt% Cr2O3 (CVO:Cr) are solved and refined. A whitlockite-like structure with five Ca sites, two-capped (Ca1 and Ca3) and mono-capped (Ca2) trigonal prisms, distorted octahedron (Ca4) and tetrahedron (Ca5), is determined for CVO:Cr. Single-crystal synchrotron X-ray diffraction analysis revealed the presence of chromium in Ca2, Ca3, Ca4 sites. In CVO:Cr, chromium has octahedral (Cr3+) and tetrahedral (Cr4+) coordination, which suggests structural superpositions of CaO8, CaO7, CaO6 and Cr3+O6 or Cr4+O4 polyhedra. X-ray diffraction, EPR and spectroscopic studies showed that green or yellow color of CVO:Cr is related to chromium valence state, Cr3+ or Cr4+, respectively. An increase in the Cr4+ concentration is accompanied by increased vacancy content in two of three vanadium sites. Structural behavior of transition metal ions with a variable formal charge (Co, Mn, Cr) in CVO structure is summarized, analyzed and discussed. Three absorption bands around 23900, 16300 and 14000 cm−1, typical for Cr3+ ions, are revealed in the UV-VIS spectra of green samples. An additional broad band with a maximum at 21254 cm−1 refers to Cr4+ ions, the appearance of which after annealing in air was established by X-ray diffraction analysis.