Mechanism Of Bond Formation Research Articles

A multiscale micromechanical model of adhesive interphase between cement paste and epoxy supported by nanomechanical evidence

Even though epoxy adhesives are used extensively in concrete structures, little fundamental research has been conducted regarding bond formation mechanisms between the adhesive and concrete substrate, which obscures our understanding of degradation mechanisms in the bonded joints. When epoxy adhesive is applied to the concrete substrate, a transition region – termed interphase – is formed between the bulk epoxy and bulk cement paste/aggregate. Properties of interphase are thought to govern the macroscale behavior and durability of epoxy-concrete bonded systems. This work proposes an elastic multiscale model of the interphase region that is based on the existing body of knowledge on the topic. Site-specific statistical nanoindentation was used to experimentally evaluate the interphase region and verify the micromechanical model. Test results indicate that mechanical properties of the interphase region are different from those of bulk epoxy and cement paste. Experimental findings agreed with the postulated multiscale interphase model.

Ab initio computational study of electronic structure part-1: reaction mechanism of peptide bond formation between amino acid alanine and glycine

The porosity of the peptide delivery pathway to the brain is hindered by the presence of tight junctions which are intercellular cadherin interactions, but this can be overcome by modulating the cadherin molecule using peptide derived synthesis, one of which is ADT-10 (Ac-QGADTPPVGV-NH2)’ where there are amino acids glycine (G) and alanine (A). Formation reaction of the peptide is one of the most important chemical reactions, one way to probe the reaction of peptide synthesis is the computational method. The purpose of this research is to determine which mechanism of the reaction is most preferred to the synthesis of peptide bond formation between alanine and glycine from four pathways of the reaction mechanism, as well as glycine and glycine from two pathway of reaction mechanisms by ab initio computational approach. The calculations were carried out by theory and basis set HF/6-31g**. The results show the most preferred reaction of peptide synthesis of amino acid glycine and alanine is on the mechanism IV which result in Ac-GA-NH2 with activation energy 759.614 kJ⋅mol−1, while in glycine and glycine is on the mechanism II with an activation energy of 933.550 kJ⋅mol−1.

Next‐generation quantum theory of atoms in molecules for the photochemical ring‐opening reactions of oxirane

AbstractThe conical intersections corresponding to the C─O and C─C ring opening were optimized and the reaction paths traversing these intersections were obtained. Investigation of the C─O ring opening revealed that when traversing the lowest energy conical intersection, the reaction path returns to the closed ring geometry. The C─O path traversing the intersection featuring torsion of terminal CH2 group however, led to a ring‐opened geometry, an H‐shift and the formation of acetaldehyde that can undergo further dissociation. The observation of different reaction paths was explained by the 3‐D paths from quantum theory of atoms in molecules (QTAIM) that defined the most preferred direction of electronic motion that precisely tracked the mechanisms of bond breaking and formation throughout the photo‐reactions. The size, orientation, and location of these most preferred 3‐D paths indicated the extent and direction of motion of atoms, bonds, and the degree of torsion or planarity of a bond indicating a predictive ability.

Theoretical and computational investigations of geometrical, electronic and spin structures of the CaMn4 OX (X = 5, 6) cluster in the Kok cycle Si (i = 0-3) of oxygen evolving complex of photosystem II.

The optimized geometries of the CaMn4 OX (X = 5, 6) cluster in the oxygen evolving complex (OEC) of photosystem II (PSII) by large-scale quantum mechanics (QM) and molecular mechanics (MM) calculations are compared with recent serial femtosecond crystallography (SFX) results for the Si (i = 0-3) states. The valence states of four Mn ions by the QM/MM calculations are also examined in relation to the experimental results by the X-ray emission spectroscopy (XES) for the Si intermediates. Geometrical and valence structures of right-opened Mn-hydroxide, Mn-oxo and Mn-peroxide intermediates in the S3 state are investigated in detail in relation to recent SFX and XES experiments for the S3 state. Interplay between theory and experiment indicates that the Mn-oxo intermediate is a new possible candidate for the S3 state. Implications of the computational results are discussed in relation to possible mechanisms of the oxygenoxygen bond formation for water oxidation in OEC of PSII.

Effect of Surface Silanol Groups on Friction and Wear between Amorphous Silica Surfaces.

Reactive molecular dynamics (ReaxFF) simulations are performed to explore the tribological behavior between fully hydroxylated amorphous silica (a-SiO2) surfaces as a function of surface silanol density. The results show that the interfacial friction and wear are greatly reduced by increasing surface silanol density, which originates from the suppression of the initial formation of interfacial Si-O-Si bridge bonds. Two different tribochemical reactions resulting in the formation of interfacial Si-O-Si bridge bonds are observed: i.e., one occurring between two silanol groups, which is insensitive to changes in silanol density, and the other occurring between a silanol group and a surface Si-O-Si bond, which is strongly suppressed with the increase of silanol density. We decouple the contributions of these two Si-O-Si bond formation mechanisms to the observed tribological behavior and find that the latter formation mechanism plays a dominant role. Furthermore, the changes in the geometry and structure of fully hydroxylated a-SiO2 surface caused by the increased surface silanol groups also play an important role in the tribochemical reactions and the tribological performance of the a-SiO2/a-SiO2 system. This work provides a deeper insight into the effect of surface silanol groups on the tribological behaviors of silicon-based materials.

Expanding the Scope of Protein Synthesis Using Modified Ribosomes.

The ribosome produces all of the proteins and many of the peptides present in cells. As a macromolecular complex composed of both RNAs and proteins, it employs a constituent RNA to catalyze the formation of peptide bonds rapidly and with high fidelity. Thus, the ribosome can be argued to represent the key link between the RNA World, in which RNAs were the primary catalysts, and present biological systems in which protein catalysts predominate. In spite of the well-known phylogenetic conservation of rRNAs through evolutionary history, rRNAs can be altered readily when placed under suitable pressure, e.g. in the presence of antibiotics which bind to functionally critical regions of rRNAs. While the structures of rRNAs have been altered intentionally for decades to enable the study of their role(s) in the mechanism of peptide bond formation, it is remarkable that the purposeful alteration of rRNA structure to enable the elaboration of proteins and peptides containing noncanonical amino acids has occurred only recently. In this Perspective, we summarize the history of rRNA modifications, and demonstrate how the intentional modification of 23S rRNA in regions critical for peptide bond formation now enables the direct ribosomal incorporation of d-amino acids, β-amino acids, dipeptides and dipeptidomimetic analogues of the normal proteinogenic l-α-amino acids. While proteins containing metabolically important functional groups such as carbohydrates and phosphate groups are normally elaborated by the post-translational modification of nascent polypeptides, the use of modified ribosomes to produce such polymers directly is also discussed. Finally, we describe the elaboration of such modified proteins both in vitro and in bacterial cells, and suggest how such novel biomaterials may be exploited in future studies.

Ru-bda: Unique Molecular Water-Oxidation Catalysts with Distortion Induced Open Site and Negatively Charged Ligands.

A water-oxidation catalyst with high intrinsic activity is the foundation for developing any type of water-splitting device. To celebrate its 10 years anniversary, in this Perspective we focus on the state-of-the-art molecular water-oxidation catalysts (MWOCs), the Ru-bda series (bda = 2,2'-bipyridine-6,6'-dicarboxylate), to offer strategies for the design and synthesis of more advanced MWOCs. The O-O bond formation mechanisms, derivatives, applications, and reasons behind the outstanding catalytic activities of Ru-bda catalysts are summarized and discussed. The excellent performance of the Ru-bda catalyst is owing to its unique structural features: the distortion induced 7-coordination and the carboxylate ligands with coordination flexibility, proton-transfer function as well as small steric hindrance. Inspired by the Ru-bda catalysts, we emphasize that the introduction of negatively charged groups, such as the carboxylate group, into ligands is an effective strategy to lower the onset potential of MWOCs. Moreover, distortion of the regular configuration of a transition metal complex by ligand design to generate a wide open site as the catalytic site for binding the substrate as an extra-coordination is proposed as a new concept for the design of efficient molecular catalysts. These inspirations can be expected to play a great role in not only water-oxidation catalysis but also other small molecule activation and conversion reactions involving artificial photosynthesis, such as CO2 reduction and N2 fixation reactions.

Cascading microstructures in aluminum-steel interfaces created by impact welding

With the growing need to develop light weight structures joining dissimilar metals is inevitable. Hence a fundamental understanding of the microstructure evolution and bond formation mechanism is necessary. In this work we probe the welded interface in aluminum and steel joined using vaporizing foil actuator welding (VFAW) a novel impact welding process. The goal of such a detailed characterization campaign is to understand the bond formation mechanism. The study shows that the interfacial microstructure has a pronounced hierarchical nature. At the macro scale, the interface is characterized by a wavy interface which is a result of extensive plastic deformation that accompanies the process. Detailed transmission electron microscopy shows evidence for the formation of a liquid film at the interface resulting in significant inter diffusion of Fe. The solidified structure at the interface consisted of crystalline α-Al and an amorphous metastable Al-Fe intermetallic compound similar to the observations in rapid solidification of Al-Fe alloys. The sub-nm scale characterization of the interface using atom probe tomography showed two distinct zones1.A magnesium (5 at.%) and oxygen (15 at.%) rich (not detectable using energy dispersive spectroscopy) which was probably from the decomposition of the surface oxide film2.The rapidly solidified reaction zone consisting of primary crystalline α-Al and an amorphous Al-Fe (15 at.%)-O (0.5 at.%)-Si (1.5 at.%).Based on these observations a mechanism for the bond formation is presented.

Surface modification of Fe3O4 nanoparticles with dextran via a coupling reaction between naked Fe3O4 mechano-cation and naked dextran mechano-anion: A new mechanism of covalent bond formation

A surface modified Fe3O4 nanoparticle with dextran, possessing a core-shell structure, was synthesized by vibration ball-milling of Fe3O4 with dextran in the solid state under vacuum. A combination of experimental results and density functional theory calculations demonstrate that the surface modified Fe3O4 nanoparticle with dextran was performed via a coupling reaction between a “naked” Fe+ atom of Fe3O4 mechano-cation and a “naked” O− atom of dextran mechano-anion, viz., a “Fe:O” bond-formation. The naked Fe+ atom of Fe3O4 mechano-cation was produced by ionic scission of FeO bond of Fe3O4 and lost an “electron pair” under the ionic scission. The naked :O− atom of dextran mechano-anion was produced by ionic scission of CO bond comprising the α-1,6 glycosidic linkage of the dextran and gained the electron pair under the ionic scission. The Fe:O bond formation, viz., a novel type covalent bond formation, was achieved via an electron pair donation from the naked :O− atom and its acceptance by the naked Fe+ atom. Consequently, a shared “electron pair” comprising the Fe:O bond was only donated from the naked :O− atom. Our work demonstrates a novel method to form covalent bond formation between metal oxides and organic polymers, and provides a novel functionalized nanoparticle.

Atomic-level understanding of interface interactions in a halloysite nanotubes–PLA nanocomposite

To understand the nature of the bonding mechanism between poly(lactic acid) (PLA) and halloysite nanotubes (HNT), a first-principles DFT study was performed on the adsorption behavior of the PLA monomer, lactic acid (LA), on the outer, inner, and edge surfaces of the HNT. The role of LA functional groups, and its orientation behavior in the formation of bonds with HNT are systematically studied. Analysis of the adsorption energy, total and partial electron density of states (DOS), electric charge transfer between LA atoms and HNT mineral surfaces shows that van der Waals attraction governs their interaction. The calculations of the most stable adsorption configurations of LA show that the predominant number of hydrogen bonds is determined by the activity of the carboxyl functional group of LA on the hydroxylated surfaces of HNT. The important role of the –OH surface groups in the mechanism of lactic acid binding has been established; their absence on the external siloxane surface significantly reduces the LA affinity for HNT. The binding energy of lactic acid on the hydroxylated internal and edge surfaces of the HNT is much higher (by about 275%) than on the external siloxane surface. Mulliken population analysis showed that the formation of a hydrogen bond with the LA atomic groups leads to a more significant redistribution of charge on the inner and edge surfaces of the HNT in comparison with its outer surface. Van der Waals attraction between the LA and HNTs, as well as hydrogen bonds, is responsible for the formation of the bonding mechanism in halloysite nanotubes-PLA nanocomposite. Our results are in accord with available literature.

Assays for dissecting the in vitro enzymatic activity of yeast Ubc7.

Ubiquitin (Ub)-mediated protein degradation is a key cellular defense mechanism that detects and eliminates defective proteins. A major intracellular site of protein quality control degradation is the endoplasmic reticulum (ER), hence the term ER-associated degradation, or endoplasmic reticulum-associated degradation (ERAD). Yeast ERAD is composed of three Ub-protein conjugation complexes, named according to their E3 Ub-protein ligase components, Hrd1, Doa10, and the Asi complex, which resides at the nuclear envelope (NE). These ER/NE membrane-associated RING-type E3 ligases recognize and ubiquitylate defective proteins in cooperation with the E2 conjugating enzyme Ubc7 and the obligatory Ubc7 cofactor Cue1. Interaction of Ubc7 with the RING domains of its cognate E3 Ub-protein ligases stimulates the formation of isopeptide (amide) Ub-Ub linkages. Each isopeptide bond is formed by transfer of an Ubc7-linked activated Ub to a lysine side chain of an acceptor Ub. Multiple Ub transfer reactions form a poly-Ub chain that targets the conjugated protein for degradation by the proteasome. To study the mechanism of Ub-Ub bond formation, this reaction is reconstituted in a cell-free system consisting of recombinant E1, Ub, Ubc7, its cofactor Cue1, and the RING domain of either Doa10 or Hrd1. Here we provide detailed protocols for the purification of the required recombinant proteins and for the reactions that produce an Ub-Ub bond, specifically, the formation of an Ubc7~Ub thiolester (Ub charging) and subsequent formation of the isopeptide Ub-Ub linkage (Ub transfer). These protocols also provide a useful guideline for similar in vitro ubiquitylation reactions intended to explore the mechanism of other Ub-conjugation systems.

A computational study on H2S release and amide formation from thionoesters and cysteine.

The recognition of the biological activity of H2S has drawn much attention to the development of biocompatible H2S release reactions. Thiol-, particularly cysteine-triggered systems which mimic the enzymatic conversion of cysteine or homocysteine to H2S have been intensively reported recently. Herein, a density functional theory (DFT) study was performed to address the reaction mechanism of H2S release and potential amide bond formation from thionoesters and cysteine to gain deeper mechanistic insights. Three possible mechanisms were considered and we found that the one starting from the nucleophilic addition of the ionized mercapto of cysteine on thionoester to generate a dithioester intermediate (Path A) is kinetically favored over the others starting from the nucleophilic addition of the amine of cysteine to generate thionoamide intermediates (Paths B and C). Dithioester then undergoes intramolecular nucleophilic addition of an amine group and the rate-limiting water-assisted proton transfer to generate a cyclic thiol intermediate, and finally affords H2S and dihydrothiazole via water-assisted elimination. The hydrolysis of thionoamide or dihydrothiazole to produce amide is highly difficult under neutral conditions but is operative under strong basic conditions, which explains the experimental observation that dihydrothiazole rather than amide is the major product. Meanwhile, the ring opening reaction of the cyclic thiol intermediate to form the more stable thionoamide is detrimental to H2S release and becomes competitive under basic conditions.

The mechanism and structure-activity relationship of amide bond formation by silane derivatives: a computational study.

The condensation of carboxylic acids and amines mediated by silane derivatives provided a straightforward and sustainable method for amide bond formation with minimal waste. However, the detailed mechanism and structure-activity relationship of substrates, the topics that are of interest for both academic and industrial applications, were not clear. Herein, a systematic computational study was conducted to solve the two questions. We found that the two previously proposed mechanisms involving intramolecular acyl transfer or silanolate were less likely because the associated silanone intermediate and zwitterion adducts were too unstable with higher overall energy barriers. By comparison, the mechanism involving deprotonation of carboxylic acids, addition of carboxylates on silane reagents, dihydrogen formation to afford an acyloxysilane intermediate, carboxylic-acid-assisted addition of amines, and concerted proton transfer/amide formation, was found to be more favorable with overall energy barriers varying between 24 and 28 kcal mol-1 for the different calculated cases. Meanwhile, the dihydrogen formation and amide formation processes are both potential rate-determining steps. Energy composition, atomic charge, and distortion-interaction analyses indicated that the steric effect of silane reagents was more important than the electronic effect, making less bulky silane reagents more reactive. On the other hand, the dihydrogen formation process was mainly controlled by the electronic effect of the substituents of carboxylic acids and amines while the amide formation process was mainly influenced by their steric effect. As a result, less bulky, less acidic alkyl carboxylic acids are more reactive than unsaturated carboxylic acids, and less bulky, medium basic primary alkyl amines are more reactive than secondary alkyl amines and primary aryl amines. The related results provided deeper mechanistic insights into the amide bond formation mediated by silane derivatives and can act as a reference for further experimental design.

Quantum mechanical tunnelling through the catalytic effects of A2451 ribosomal residue during a stepwise peptide bond formation.

The search for the mechanism of ribosomal peptide bond formation is still ongoing. Even though the actual mechanism of peptide bod formation is still unknown, the dominance of proton transfer in this reaction is known for certain. Therefore, it is vital to take the quantum mechanical effects on proton transfer reaction into consideration; the effects of which were neglected in all previous studies. In this study, we have taken such effects into consideration using a semi-classical approach to the overall reaction mechanism. The M06-2X density functional with the 6-31++G(d,p) basis set was used to calculate the energies of the critical points on the potential energy surface of the reaction mechanism, which are then used in transition state theory to calculate the classical reaction rate. The tunnelling contribution is then added to the classical part by calculating the transmission permeability and tunnelling constant of the reaction barrier, using the numerical integration over the Boltzmann distribution for the symmetrical Eckart potential. The results of this study, which accounts for quantum effects, indicates that the A2451 ribosomal residue induces proton tunnelling in a stepwise peptide bond formation.

Unprecedented Mechanism of an Organocatalytic Route to Conjugated Enynes with a Junction to Cyclic Nitronates

Conjugated enynes as well as cyclic nitronates are crucial building blocks for numerous natural products and pharmaceuticals. However, so far, no common and metal‐free synthetic route to both conjugated enynes and cyclic nitronates has been reported. Herein, in situ NMR, labelling studies and theoretical calculations were combined to investigate the mechanism of the unusual triple bond formation towards conjugated enynes. Starting from nitroalkene dimers, first an isoxazolidine‐2,5‐diol derivative is formed as central intermediate. From this, enynes were generated by a combination of oxidation, dehydration, and retro 1,3‐dipolar cycloaddition, whereas for nitronates a base induced intramolecular reorganization is proposed. While the product distribution could be controlled and high yields of nitronate were achieved, only medium to good yields for enynes were obtained due to polymerization losses. Nevertheless, we hope that these mechanistic investigations may provide a basis for further developments of organocatalytic or metal‐free preparations of conjugated enynes and nitronates.

Understanding the kinetics and molecular mechanism of unimolecular gas phase thermal decomposition of the α-ketoester methyl benzoylformate using RRKM and BET theories

The RRKM calculation and bonding evolution theory analysis coupled with quantum theory of atoms in molecules have been used to investigate kinetics and molecular mechanism of gas phase thermal decomposition of methyl benzoylformate. The pressure-dependent rate coefficients, by applying different collisional efficiency values, indicated that the atmospheric pressure is in high-pressure limit of fall-off curve and low-pressure limit rate coefficients are in the range of 10−13-10−12 cm3 molec−1 s−1. Temperature dependence of high-pressure limiting of rate coefficient over the temperature range 733 ± 20% K was estimated to be k∞RRKM(CBS-QB3)=2.92×1013s-1exp(227.4kJmol-1/RT) and k∞RRKM(PBE1PBE)=2.67×1013s-1exp(232.8kJmol-1/RT). Topological analysis of electron localization function and electron density at the B3LYP/6-311G(d,p) level reveal that the reaction can be occurred as going through seven turning points defined as methyl benzoylformate 8-CF†FF†TSFC†[CF†]-0: methyl benzoate + carbon monoxide. The molecular mechanism can be categorized in three fundamental sections A) heterolytic rupture of O3C8 bond and detachment of methoxy part; B) formation of O3C7 bond via donation bond formation mechanism; and C) heterolytic rupture of C7C8 bond and detachment of carbon monoxide. The electron density ρ(3,−1)(r) in the region of bond forming and breaking increases and decreases along the reaction course to reflect bond strengthening and weakening, respectively. AIM parameters revealed that so long as chemical bonds are unformed/ruptured, interactions at related BCPs are covalence in nature, otherwise the nature of chemical bonds are strong shared covalence.

Unravelling the structure of glycosyl cations via cold-ion infrared spectroscopy

Glycosyl cations are the key intermediates during the glycosylation reaction that covalently links building blocks during the synthetic assembly of carbohydrates. The exact structure of these ions remained elusive due to their transient and short-lived nature. Structural insights into the intermediate would improve our understanding of the reaction mechanism of glycosidic bond formation. Here, we report an in-depth structural analysis of glycosyl cations using a combination of cold-ion infrared spectroscopy and first-principles theory. Participating C2 protective groups form indeed a covalent bond with the anomeric carbon that leads to C1-bridged acetoxonium-type structures. The resulting bicyclic structure strongly distorts the ring, which leads to a unique conformation for each individual monosaccharide. This gain in mechanistic understanding fundamentally impacts glycosynthesis and will allow to tailor building blocks and reaction conditions in the future.

Manufacturing and Characterization of Twin‐Roll Cast Aluminum‐Steel Clad Strips

The manufacturing of clad strips by means of twin‐roll casting is a prospective trend regarding the production of lightweight materials. This study is dedicated to an analysis of bond formation conditions during the twin‐roll casting of clad strips of aluminum EN AW‐1070 and an austenitic stainless steel 1.4301. The procedures of steel substrate preparation and their influence on the diffusion bond are investigated. These include surface pre‐treatment of the steel substrate by means of mechanical grinding and laser irradiation as well as its pre‐heating. Using the different sets of process parameters, the clad strips with a thickness of 2.5 mm are manufactured and characterized. Light and electron microscopy are used to characterize the microstructure of the aluminum layer and the bond zone and to investigate the mechanism of bond formation. The evaluation of the strips’ properties is carried out by means of adhesive tensile tests, peeling tests, uniaxial tensile tests, and fatigue tests. The influence of each of the substrate preparation methods as well as post heat treatment on the parameters of bond zone and the mechanical properties of the clad strip is investigated. The implementation of the investigated manufacturing method allows producing thin clad strips with excellent characteristics.

Investigation of Interfacial Layer for Friction Stir Scribe Welded Aluminum to Steel Joints

Friction stir scribe (FSS) welding as a recent derivative of friction stir welding (FSW) has been successfully used to fabricate a linear joint between automotive Al and steel sheets. It has been established that FSS welding generates a hook-like structure at the bimaterial interface. Beyond the hook-like structure, there is a lack of fundamental understanding on the bond formation mechanism during this newly developed FSS welding process. In this paper, the microstructures and phases at the joint interface of FSS welded Al to ultra-high-strength steel were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that both mechanical interlocking and interfacial bonding occurred simultaneously during the FSS welding process. Based on SEM observations, a higher diffusion driving force in the advancing side was found compared to the retreating side and the scribe swept zone, and thermally activated diffusion was the primary driving force for the interfacial bond formation in the scribe swept region. The TEM energy-dispersive X-ray spectroscopy (EDXS) revealed that a thin intermetallic compound (IMC) layer was formed through the interface, where the thickness of this layer gradually decreased from the advancing side to the retreating side owing to different material plastic deformation and heat generations. In addition, the diffraction pattern (or one-dimensional fast Fourier transform (FFT) pattern) revealed that the IMC layer was composed of Fe2Al5 or Fe4Al13 with a Fe/Al solid solution depending on the weld regions.

Modified equation for particle bonding area and strength with inclusion of powder fragmentation propensity

The paper considers a novel, modified equation for evaluation of relationship between tablet tensile strength, bonding area and bonding strength with inclusion of fragmentation as particle deformation mechanism. Four types of lactose particles for direct compression were assessed for their micromeritic and mechanical properties (compressibility and compactibility), with particular focus on fragmentation behaviour, bonding area and bonding strength. Compressibility properties were assessed using three established models. Walker and Kuentz-Leuenberger models distinguished lactose plastic properties more effectively in contrast to the Heckel model. Spherical agglomerates of lactose were most prone to fragmentation as determined with the fragmentation propensity coefficient and the number of interparticulate bonds. Fragmentation, together with plastic deformation were found to be the governing factors for tablet tensile strength in α-lactose samples, while high bonding force primarily controlled the tablet tensile strength of anhydrous lactose. Tensile strength of all lactose tablets showed best correlation to the ratio of fragmentation propensity and Walker compressibility coefficient, which is proposed as better deformation index, intended to describe the overall deformation properties of lactose more precisely. A novel expression for determining bonding area is proposed, established on the enhanced deformation index, which includes both plastic deformation and fragmentation as bond formation mechanisms.