Specific Structural Features Research Articles

Exploring structural origins responsible for the exceptional mechanical property of additively manufactured 316L stainless steel via in-situ and comparative investigations

The laser beam powder-bed-fusion (PBF-LB) technique offers the possibility to fabricate metallic materials with unparalleled mechanical properties. However, due to the complexity of nonequilibrium solidification structures, untangling the role of specific structural features in influencing mechanical properties through post-mortem analysis remains a significant challenge. Here, we tracked the complete evolution of deformation microstructures in PBF-LB 316L stainless steel (SS) and conventionally manufactured (CM) counterparts using in-situ electron channeling contrast imaging (ECCI) in conjunction with high-angular resolution electron backscatter diffraction (HR-EBSD). Our findings underscore the importance of the intrinsic dislocation configuration, i.e., faulted dipole, in modulating the plastic deformation behaviors of the PBF-LB sample. The periodic arrangement of faulted dipoles triggers a widespread activation of stacking faults (SFs) with extremely fine spacing at the yielding stage, resulting in a high passing stress (∼433 MPa) that is responsible for the high yield strength. Meanwhile, such configuration facilitates uniform plastic deformation and mediates twinning propensity, thereby alleviating stress concentrations and enhancing ductility. Moreover, by correlating the mechanical response with microstructural evolution, we establish a modified model for multiple strengthening mechanisms in the PBF-LB sample. Additionally, we examine the effect of nonequilibrium solidification structures on the strain rate sensitivity of PBF-LB samples. Taking 316L SS as an exemplar, our results extend the current understanding of the structural origins responsible for the exceptional mechanical properties of metals manufactured by PBF-LB.

Characterizing Interconnection Networks in Terms of Complexity via Entropy Measures

One of the most recent advancements in graph theory is the use of a multidisciplinary approach to the investigation of specific structural dependent features, such as physico-chemical properties, biological activity and the entropy measure of a graph representing objects like a network or a chemical compound. The ability of entropy measures to determine both the certainty and uncertainty about objects makes them one of the most investigated topics in science along with its multidisciplinary nature. As a result, many formulae, based on vertices, edges and symmetry, for determining the entropy of graphs have been developed and investigated in the field of graph theory. These measures assist in understanding the characteristics of graphs, such as the complexity of the networks or graphs, which may be determined using entropy measures. In this paper, we derive formulae of entropy measures of an extensively studied family of the interconnection networks and classify them in terms of complexity. This is accomplished by utilizing all three tools, including analytical formulae, graphical methods and numerical tables.

Multi-scale characterization of Developmental Defects of Enamel and their clinical significance for diagnosis and treatment.

Developmental Defects of Enamel (DDE) such as Dental Fluorosis (DF) and Molar Incisor Hypomineralization (MIH) are a major public health problem. Their clinical aspects are extremely variable, challenging their early and specific diagnosis and hindering progresses in restorative treatments. Here, a combination of macro-, micro- and nano-scale structural and chemical methods, including, among others, Atom Probe Tomography recently applied on tooth enamel, were used to study and compare MIH, DF and healthy teeth from 89 patients. Globally, we show that DF is characterized by an homogenous loss of mineral content and crystallinity mainly disrupting outside layer of enamel, whereas MIH is associated with localized defects in the depth of enamel where crystalline mineral particles are embedded in an organic phase. Only minor differences in elemental composition of the mineral phase could be detected at the nanoscale such as increased F and Fe content in both severe DDE. We demonstrate that an improved digital color measurement of clinical relevance can discriminate between DF and MIH lesions, both in mild and severe forms. Such discriminating ability was discussed in the light of enamel composition and structure, especially its microstructure, organics presence and metal content (Fe, Zn). Our results offer additional insights on DDE characterization and pathogenesis, highlight the potentiality of colorimetric measurements in their clinical diagnosis and provide leads to improve the performance of minimally invasive restorative strategies. STATEMENT OF SIGNIFICANCE: Developmental Defects of Enamel (DDE) are associated to caries and tooth loose affecting billions of people worldwide. Their precise characterization for adapted minimally invasive care with optimized materials is highly expected. Here In this study, first we propose the use of color parameters measured by a spectrophotometer as a means of differential clinical diagnosis. Second, we have used state-of-the-art techniques to systematically characterize the structure, chemical composition and mechanical optical properties of dental enamel teeth affected by two major DDE, Dental Fluorosis (DF) or Molar Incisor Hypomineralization (MIH). We evidence specific enamel structural and optical features for DF and MIH while chemical modifications of the mineral nanocrystals were mostly correlated with lesion severity. Our results pave the way of the concept of personalized dentistry. In the light of our results, we propose a new means of clinical diagnosis for an adapted and improved restoration protocol for these patients.

A study on the ground loss and foundation coupling loss for railway vibration prediction in greater Perth area of Western Australia

Railway noise and vibration have emerged as significant concerns affecting the well-being of residents living in proximity to railway tracks and the structural integrity of nearby infrastructure. As such, accurate and reliable predictions of railway vibration levels are necessary in order to properly assess the risks and develop effective mitigations. The propagation of railway vibration from the source to the receiving point involves a complex process, wherein ground loss and foundation coupling loss play crucial roles. Therefore, comprehensive capture of these factors is necessary for improving the accuracy of railway vibration prediction. This paper presents a study focused on the measurements of ground damping loss and foundation coupling loss in great Perth area of Western Australia. The measurements have been undertaken in generally sandy soil conditions. The foundation coupling loss was primarily measured at single-storey residential dwellings. The collected field data were subsequently analyzed to identify the characteristics of ground loss and foundation coupling loss. The study revealed that ground loss and foundation coupling loss exhibited variability dependent on the specific location, ground conditions, and structural characteristics of the dwellings. These measured results can serve as input for modeling efforts, thereby enabling more accurate prediction of railway vibration levels. Furthermore, the study provides valuable insights into the characterization of vibration propagation in sandy soils.

Early code-switches in young Russian bilingual siblings

The number of bilinguals and multilinguals of all age groups, including the youngest ones, constantly grows in many countries of the world, which explains the topicality of the study. While researchers explore various aspects of bilingual development, linguists concentrate their efforts on the analysis of bilingual speech, including code-switches. The author deals with Russian-English code-switches in the utterances of two siblings at the earliest stages of their bilingual development - before they were 36 months old. The children had acquired two languages since their first month in a monoethnic Russian family, their first language being Russian and their second (non-native) language being English. The aim of the study is to reveal specific structural, semantic, and pragmatic characteristics of mixed utterances observed in early code-switches of the siblings. The author argues that children’s code-switches at the earliest stages within one family reflect specific features of the communicative situations where children have to cope with the choice between the two languages spoken by their adult interlocutors. It is shown that the application of the Matrix Language Frame Model to the analysis of early childhood bilingual speech is possible, but has several restrictions and limitations related to incomplete and imperfect acquisition of both grammars. The originality of the research is not only in the use of specific data (the earliest stage of bilingual speech observed in simultaneous Russian-English dual-language development), but also in the employment of the Matrix Language Frame Model to study them. This work can contribute to the research of typical features of emerging code-switches in developmental perspective.

Predation pressure by arthropods, birds, and rodents is interactively shaped by tree species richness, vegetation structure, and season

Tree species richness, forest structure, and seasonal fluctuations between rainy and dry seasons can strongly affect trophic interactions in forest ecosystems, but the inter- and scale dependence of these variables remains unclear. Using artificial caterpillars (~18,000 replicates), we analyzed predation pressure by arthropods, birds, and rodents along a tree species richness gradient across seasons in a subtropical tree diversity experiment (BEF-China). The aim of the study was to test if forest structure, in addition to tree species richness, has an effect on predation pressure and to further specify which structural variables are important in driving predation. We assessed the effects of tree species richness and forest structure at the plot and local neighborhood levels. We also included fine-scale placement covariates, plot size, and topographical covariates of the study site. Forest structure and tree species richness independently and interactively affected predation pressure. The spatial scale was an important determinant for tree species richness and structural effects, extending from within plot scales to the overall heterogeneity of the plots’ surrounding environment. For example, the effect of branch density in the local neighborhood depended on both surrounding tree species richness and plot-level vegetation density. Similarly, visibility-enhancing factors increased attacks by arthropods (lack of branches in close surroundings) and by birds (open area), depending on the surrounding vegetation. A comparison of structural measures showed that predation pressure can be addressed in much greater detail with multiple specific structural features than with overall forest complexity. Seasonal change also affected predation pressure, with foliage being a stronger attractant in spring, but also by presumable topography-driven study plot differences in sun exposure and humidity between rainy and dry seasons. Our study demonstrates that predation pressure is not simply a function of tree species richness or structure but is shaped by the interplay of structural elements, spatial scale, and seasonal dynamics along gradients of tree species richness and forest structure. The structural and seasonal effects are important to take into account when addressing how current and future biodiversity loss may change top‐down control of herbivory and overall ecosystem functioning.

Specific features of the narrative structure in L. N. Tolstoy’s story "The Forged Coupon" (to the 195th anniversary of the birth)

The subject of the study is "The Forged Coupon", one of the later stories by L. N. Tolstoy. The article considers how Tolstoy’s main discoveries are implemented in the text from the standpoint of constructing a literary narrative. The article presents the novella from the perspective of the writer’s creative mastery evolution. The research employed end-to-end text sampling, semasiological analysis based on lexicographic sources, subtext explication techniques. The study also used psycholinguistic approaches to examine the emotional pattern of the text. The ideological plane of the content is interpreted by identifying key words (heuristemes). The article characterises the dynamics of the narration pace, the nature of the development of the compositional plot lines. It also reveals fragments of a convoluted, compressed narrative and compositional parts based on precedent texts. The study demonstrates L. N. Tolstoy’s techniques for semantic extension of vocabulary and attaching additional connotations to the usual meanings of lexemes. In addition, the paper characterises the forms of syntactic constructions and a special kind of Tolstoy’s tale (or skaz), as well as reveals the semantic charge of foreign inclusions. The research shows the continuity between the mature and late Tolstoy’s style in highlighting a significant artistic detail, embodying the inconsistency of human thinking and emotional states. The article evaluates the influence of the late Tolstoy’s style on the formation of artistic and literary aesthetics of the 20th century.

Multi-level adaptive perception guidance based infrared and visible image fusion

The current constraint rules of end-to-end infrared and visible image fusion (IVIF) networks based on deep learning solely focus on the pixel level, disregarding the consideration of deep features and global information. To address this limitation, this paper proposes an multi-level adaptive perception-guided image fusion approach, named MAPFusion. The main idea is to design a specific network structure and use features to guide the training of the network. Specifically, on the one hand, a new loss function strategy is designed, which combines pixel-level, structure-level, and feature-level strategies to comprehensively enhance the information of the fused image. In particular, the multi-level adaptive perceptual loss is introduced as a feature-level strategy, which preserves both low-level positional data and high-level semantic data by constraining the original image and fused image features. Moreover, adaptive weights are constructed using the information measure between feature maps, which measure the degree of information preservation of different source images. On the other hand, a new fusion network is proposed, which uses the improved U-Net structure to extract the multi-scale features of the image, and adds the Atrous Spatial Pyramid Pooling (ASPP) to the specific network layer, which can increase the receptive field and effectively take advantage of the global information of the image. Comparative experiments demonstrate that the proposed method effectively utilizes the information existing in infrared and visible images, resulting in superior visual quality and objective evaluation compared to SOTA algorithms. Ablation and supplementary experiments further validate the rationality of the proposed method and its potential for advanced vision tasks.

Understanding Photo(electro)catalysts for Energy Conversion via Operando Functional Imaging.

Understanding the fundamental processes of charge carrier generation, separation, transport, and reactivity on the surface of semiconductors is crucial for the rational design of high-performance photo(electro)catalysts for various energy conversion applications. Nevertheless, the ubiquitous and intricate heterogeneity exhibited by individual catalysts poses a significant obstacle to achieving a comprehensive understanding of the structure-function relationships using bulk-level, ensemble-averaged characterizations. This review highlights the emerging operando imaging techniques capable of providing local functional information, such as surface photovoltage, photoluminescence, charge carrier reaction rate, and photocurrent, at the single particle to subparticle level. By establishing correlations between the acquired local functional information and the specific structural characteristics of the catalyst, a quantitative, holistic understanding of the structure-function relationship in photo(electro)catalysts can be achieved. This understanding can serve as a foundation for guiding the design of photocatalysts with enhanced energy conversion performance.

Superior Rate Capability of Small Regenerated Graphite Particles Induced by Homogeneously Distributed Current Density Derived from Cracks and Intrinsic Defects.

As spent batteries can be considered as alternative raw sources of electrode materials; the development of regeneration techniques for spent graphite becomes key to realizing economic and environmental sustainability. Herein, the reutilization of small spent graphite particles is domonstrateddue to their special structural characteristics, which may directly contribute to the improvement of lithiation kinetics and high-rate charging during long-term cycling. Such intrinsic defects and external cracked channels may be introduced by the aging of intrinsic bulk structure and exfoliation of surface structure. On account of these potential advantages, a carbonized polypyrrole layer on sieved small graphite particles is developed to obtain superior rate performance. The coated amorphous/graphitic layer could repair the exposed edge and basal plane, and significantly facilitate Li ion diffusion during fast charging. Moreover, the enhanced performance may favor the improved homogeneity of current density distribution during fast charging, which is confirmed by a porous electrode model. The regenerated graphite with a disorder/order coating layer could effectively regulate the Li+ transport channel, exhibiting a high specific capacity at high-rate charging (102.7 mAh g-1 at 4 C after 500 cycles) without severe Li plating. This work provides an opportunity to utilize spent graphite in fast-charging batteries.

How brain structure relates to psychopathology across diagnoses in pre‐adolescents

Using data from the federal government's Adolescent Brain Cognitive Development (ABCD) study, researchers have identified specific brain structure features that might contribute to transdiagnostic (across diagnostic categories) psychopathology development in preadolescence. The study found that children with smaller total brain volume and surface area may be vulnerable to persistent general psychopathology during preadolescence. “Cortical thinning reflective of pruning and myelination in sensorimotor and temporal brain regions specifically may protect against increases in internaliz‐ing, but not general psychopathology, during preadolescence,” according to the study. In general, structural neural alterations have been associated with the “p factor” (higher “p” scores are associated with developmental problems and other issues, but not specifically related to diagnoses). However, less is known about how the brain al‐terations relate within time in an individual, especially during preadolescence, when many neurodevelopmental changes are taking place. This study looked at the trajectory of the p factor and specific forms of psychopathology over 2 years in 9,220 preadolescents (aged 9–10 years at baseline). The study found that smaller volume and surface area of the brain, but not thickness, were associated with higher p factor scores which persisted over time in between‐person (how individuals differ) but not within‐person (how change occurs in a particular individual) p factor scores. “Lower baseline cortical thickness was associated with steeper decreases in internalizing psychopathology, which was driven by lower thickness within sensorimotor and temporal regions.” [Romer, A. L., Ren, B., Pizzagalli, D. A. (2023, Feb 9). Brain structure relations with psychopathology trajectories in the Adolescent Brain Cognitive Development Study. J Am Acad Child Adolesc Psychiatry, S0890‐8567(23)00057‐6. http://doi.org/10.1016/j.jaac.2023.02.002.]

Unusual structural and functional features of TpLRR/BspA-like LRR proteins

Leucine Rich Repeat (LRR) domains, are present in hundreds of thousands of proteins across all kingdoms of life and are typically involved in protein–protein interactions and ligand recognition. LRR domains are classified into eight classes and when examined in three dimensions seven, of them form curved solenoid-like super-helices, also described as toruses, with a beta sheet on the concave (inside) and stacked alpha-helices on the convex (outside) of the torus. Here we present an overview of the least characterized 8th class of LRR proteins, the TpLRR-like LRRs, named after the Treponema pallidum protein Tp0225. Proteins from the TpLRR class differ from the proteins in all other known LRR classes by having a flipped curvature, with the beta sheet on the convex side of the torus and irregular secondary structure instead of helices on the opposite, now concave site. TpLRR proteins also present highly divergent sequence pattern of individual repeats and can associate with specific types of additional domains. Several of the characterized proteins from this class, specifically the BspA-like proteins, were found in human bacterial and protozoan pathogens, playing an important role in the interactions between the pathogens and the host immune system. In this paper we surveyed all existing experimental structures and selected AlphaFold models of the best-known proteins containing this class of LRR repeats, analyzing the relation between the pattern of conserved residues, specific structural features and functions of these proteins.

Structure-Activity Relationships of Cationic Lipidoids against Escherichia coli.

Membrane-active molecules provide a promising strategy to target and kill pathogenic bacteria. Understanding how specific molecular features drive interactions with membrane components and subsequently cause disruption that leads to antimicrobial activity is a crucial step in designing next-generation treatments. Here, we test a library of lipid-like compounds (lipidoids) against Gram-negative bacteria Escherichia coli to garner in-depth structure-activity relationships using antimicrobial assays. Modular lipidoid molecules were synthesized in high-throughput, such that we could analyze 104 compounds with variable combinations of hydrophobic tails and cationic headgroups. Antibacterial activity was strongly correlated to specific structural features, including tail hydrophobicity and headgroup charge density, and also to the overall molecular shape and propensity for self-assembly into curved liquid crystalline phases. Dye permeabilization assays showed that E. coli membranes were permeabilized by lipidoids, confirming their membrane-active nature. The reduced permeabilization, as compared to Gram-positive Bacillus subtilis, alludes to the challenge of permeabilizing the additional outer membrane layer of E. coli. The effect of headgroup solubility in gemini-type lipidoids was also demonstrated, revealing that a headgroup with a more hydrophilic spacer between amine groups had enhanced activity against B. subtilis but not E. coli. This provides insight into features enabling outer membrane penetration and governing selectivity between bacterial species.

Molecular basis of Mg2+ permeation through the human mitochondrial Mrs2 channel

Mitochondrial RNA splicing 2 (Mrs2), a eukaryotic CorA ortholog, enables Mg2+ to permeate the inner mitochondrial membrane and plays an important role in mitochondrial metabolic function. However, the mechanism by which Mrs2 permeates Mg2+ remains unclear. Here, we report four cryo-electron microscopy (cryo-EM) reconstructions of Homo sapiens Mrs2 (hMrs2) under various conditions. All of these hMrs2 structures form symmetrical pentamers with very similar pentamer and protomer conformations. A special structural feature of Cl−-bound R-ring, which consists of five Arg332 residues, was found in the hMrs2 structure. Molecular dynamics simulations and mitochondrial Mg2+ uptake assays show that the R-ring may function as a charge repulsion barrier, and Cl− may function as a ferry to jointly gate Mg2+ permeation in hMrs2. In addition, the membrane potential is likely to be the driving force for Mg2+ permeation. Our results provide insights into the channel assembly and Mg2+ permeation of hMrs2.

5,6-Di-hydro-1,4-dithiine-2,3-di-carb-oxy-lic anhydride.

In the title com-pound (systematic name: 2,3-di-hydro-1,4-dithiino[2,3-c]furan-5,7-dione), C6H4O3S2, the observed geometry agrees well with those of its phthalamide, thieno and hy-droxy analogs, and with a calculated geometry obtained by density functional theory (DFT) calculations. Specific structural features are an S-C-C-S torsion angle of -70.39 (17)° and S-C bonds to sp 2-hybridized C atoms approximately 0.1 Å shorter than those to sp 3-hybridized C atoms. Unlike the extended structures of the analogs, there are no directed inter-molecular inter-actions and the head-to-tail rows of mol-ecules that are a prominent structural motif of the packing can be rationalized in terms of optimized dipole-dipole inter-actions.

Structural Design of Intelligent Reversible Two-Way Structural Color Films.

Structural color always shows a reversible switch between reflection and transmission states when viewed from different angles, attracting increasing attention in display applications. However, this switching between reflection and transmission states of structural color suffers from the inherent lack of autonomous regulation, which is unmanageable in the case of different application scenarios. Here, we design an intelligent two-way structural color film which can reversibly change its color when applied with an extra stimulation such as voltage, heat signal, or light. A special structural feature contains a traditional photonic crystal film of polystyrene (PS) microspheres assembled by smart windows. Remarkably, our structural color film shows a prominent polarization sensitivity, and the angle dependence of the structural color broadens the gamut of display color demonstrated by both finite element theoretical analysis and experimental observation. Prospectively, this hierarchically designed film provides a promising pathway toward next-generation multicolor displays and smart windows.

3D printed hierarchical interpenetrating phase composites with multi-scale mechanical energy absorption mechanisms

Lightweight, strong, and energy-absorbing materials are highly sought after in practical engineering applications. To this end, interpenetrating phase composites (IPC) stand as a novel class of composite materials to better leverage the properties of their constituents. Their structural design, however, has been limited to only specific structural features at a certain length scale in the existing studies. Inspired by the hierarchical composite materials in nature, this work proposes a novel concept of hierarchical interpenetrating phase composites (HIPC) by polymer infiltration into 3D printed hierarchical porous ceramic lattices. The hierarchical porous alumina lattices have up to three levels of porosity, including 3D printed macropores (≈300 μm), emulsion-templated micropores (≈10 μm), and sub-micropores (<1 μm) from partial sintering. Upon epoxy infiltration, three-level HIPC is constructed with hierarchically incorporated epoxy domains and alumina-epoxy interfaces, which leads to its unique multi-scale mechanical energy absorption mechanisms. Featuring a particularly porous and lightweight ceramic lattice, three-level HIPC exhibits an excellent combination of high specific compressive strength (64.6 kN m/kg), specific flexural strength (39.2 kN m/kg), and SEA (18.4 kJ/kg). In addition, even with a low ceramic content, three-level HIPC can effectively enhance the thermal conductivity via its hierarchically continuous ceramic microstructure. Therefore, our three-level HIPC has demonstrated impressive mechanical and thermal enhancement with its exquisite hierarchical architecture. The hierarchical structural engineering approach also represents a paradigm shift from constructing single-scale IPCs to multi-scale HIPCs and can be extended to other material combinations for high-performance structural and functional materials.

A mechanistic inquiry into the applicability of permanganate oxidizable carbon as a soil health indicator

AbstractWe determined the characteristics that render organic matter responsive to dilute permanganate oxidation to find a mechanistic explanation for the frequently observed responsiveness of permanganate oxidizable carbon (PoxC) to changes in soil health. We conclude that PoxC is primarily a measurement of phenolic and polyphenolic structures rather than of compounds traditionally viewed as preferred microbial food. Upon subjecting pure compounds to the PoxC method, we found that the susceptibility of organic molecules to permanganate oxidation was determined by the presence of specific structural features abundant in phenolic compounds, which were highly reactive (3–98 mg PoxC·g−1 C), and in a subset of low‐molecular‐weight organic acids (0–180 mg PoxC·g−1 C). In comparison, proteins were minimally reactive (0–13 mg PoxC·g−1 C) and carbohydrates were unreactive when subjected to the PoxC method. Permanganate reactivity was not found to be a predictor of decomposability in biosolids through the mirroring of C:N ratio. However, permanganate reactivity increased up to 27% throughout the decomposition process. We suggest a reinterpretation of the mechanisms that render PoxC useful as a soil health indicator. Rather than representing a preferred microbial food source, PoxC measures a carbon fraction with unique molecular properties that may be an indicator of plant‐mediated soil processes. Our research corroborates the usefulness of PoxC as a soil health indicator, albeit for entirely different reasons than previously assumed. This opens exciting avenues of further inquiry and sets the stage for intensified investigations into the general role of polyphenolic compounds in soil health.

Mutations observed in somatic evolution reveal underlying gene mechanisms

Highly sensitive DNA sequencing techniques have allowed the discovery of large numbers of somatic mutations in normal tissues. Some mutations confer a competitive advantage over wild-type cells, generating expanding clones that spread through the tissue. Competition between mutant clones leads to selection. This process can be considered a large scale, in vivo screen for mutations increasing cell fitness. It follows that somatic missense mutations may offer new insights into the relationship between protein structure, function and cell fitness. We present a flexible statistical method for exploring the selection of structural features in data sets of somatic mutants. We show how this approach can evidence selection of specific structural features in key drivers in aged tissues. Finally, we show how drivers may be classified as fitness-enhancing and fitness-suppressing through different patterns of mutation enrichment. This method offers a route to understanding the mechanism of protein function through in vivo mutant selection.

Enzyme systems for fragmentation of the rhamnogalacturonan sites main chains in plant tissue protopectin complex

Special features of the protopectin complex structure of plant tissue suggest the necessity of performing point destruction of certain glycoside bonds in the structure of rhamnogalacturonan polymer chains for industrial production of pectin. These chains include homogalacturonan sites and branching zones. As the homogalacturonan fragments of the protopectin complex carry the main functional load, glycoside bonds between residues of rhamnose and galacturonic acid are targeted bonds. For their directional destruction, it is most expedient to use enzymes of lyase and hydrolase action. The aim of this review is to systemize notions of molecular specific features of enzymes of lyase and hydrolase action that catalyze the process of enzymatic destruction of the rhamnogalacturonan main chain. The paper examines systematics of lyase and hydrolase enzymes by mechanism of destruction of glycoside bonds and by molecular structure. It is shown that the classification data intercross, as a result, each family can include one or several enzyme groups. The review shows the main structural difference of enzymes of lyase and hydrolase action that consists in the obligatory presence of Ca2+ cations in the composition of lyase enzymes. These cations take part in stabilization of conformation of the enzyme molecule and in the catalytic process per se blocking the residue of galacturonic acid. Ca2+ cations are absent in the composition of targeted hydrolase enzymes. Molecular specific features of lyase enzymes determine sensitivity of their catalytic activity to the presence of Ca2+ cations in the system. Exceeding certain concentration can lead to the antagonistic effect. There is no unambiguous idea of this regarding hydrolase enzymes. The review demonstrates the necessity of studying approaches to assessment of expediency of preliminary partial removal of cations from the substrate.