Fragmentation Chain Research Articles

Statistical potentials from the Gaussian scaling behaviour of chain fragments buried within protein globules.

Knowledge-based approaches use the statistics collected from protein data-bank structures to estimate effective interaction potentials between amino acid pairs. Empirical relations are typically employed that are based on the crucial choice of a reference state associated to the null interaction case. Despite their significant effectiveness, the physical interpretation of knowledge-based potentials has been repeatedly questioned, with no consensus on the choice of the reference state. Here we use the fact that the Flory theorem, originally derived for chains in a dense polymer melt, holds also for chain fragments within the core of globular proteins, if the average over buried fragments collected from different non-redundant native structures is considered. After verifying that the ensuing Gaussian statistics, a hallmark of effectively non-interacting polymer chains, holds for a wide range of fragment lengths, although with significant deviations at short spatial scales, we use it to define a 'bona fide' reference state. Notably, despite the latter does depend on fragment length, deviations from it do not. This allows to estimate an effective interaction potential which is not biased by the presence of correlations due to the connectivity of the protein chain. We show how different sequence-independent effective statistical potentials can be derived using this approach by coarse-graining the protein representation at varying levels. The possibility of defining sequence-dependent potentials is explored.

Columnar dipolar clusters defying gravity.

A striking and highly versatile feature of magnetic (nano)particles is their ability to be manipulated at will at a distance by external fields. In this paper, the influence of gravity on the self-assembly of dipolar particles near a surface in the presence of a strong vertical magnetic field is investigated theoretically. A rich ground-state phase diagram stems from the effects of the number of particles N and gravity. Two distinct regimes are discovered for the gravity-mediated breakup of a standing chain. When N is small, there is a chain fragmentation (with two widely separated repulsive chain fragments) above a critical value for the gravity, whereas for higher chains, ribbonization (with two cohesive chain fragments) sets in. In both scenarios, simple algebraic decays for the transition gravity as a function of N are analytically predicted and accurately corroborate the exact numerical results. Further intricate chain fragmentations and internal ribbon transformations operate upon further increasing the gravity until all N constitutive particles lie on the surface. Our findings shed additional light on various recent experiments and computer simulations on magnetic colloids and granular media.

Interpolymer Complexes of Poly(methacryloyloxyethyl phosphorylcholine) and Polyacids.

It has been shown that macromolecules of poly(methacryloyloxyethyl phosphorylcholine) can form hydrogen bonded interpolymer complexes with homo- and copolymers of carboxylic acids and with poly(vinylphosphonic) acid in aqueous solutions. Polarized luminescence and IR spectroscopy were applied in the investigation. Nanosecond relaxation times characterizing the mobility of the chain fragments for the initial luminescent labeled polymers were determined and their changes by a factor of 2–50 were established during the formation of an interpolymer complex. Hydrogen bonds play a dominant role in the formation of these complexes. Hydrophobic interactions serve as an additional stabilizing factor. It is established that poly(methacryloyloxyethyl phosphorylcholine)/poly(vinylphosphonic acid) complex forms a looser structure in comparison with those for polycarboxylic acids as result of electrostatic repulsion between charged groups.

Capillary Sodium Dodecyl Sulfate Agarose Gel Electrophoresis of Proteins

Capillary sodium dodecyl sulfate gel electrophoresis has long been used for the analysis of proteins, mostly either with entangled polymer networks or translationally cross-linked gels. In this paper capillary agarose gel electrophoresis is introduced for the separation of low molecular weight immunoglobulin subunits. The light (LC~24 kDa) and heavy (HC~50 kDa) chain fragments of a monoclonal antibody therapeutic drug were used to optimize the sieving matrix composition of the agarose/Tris-borate-EDTA (TBE) systems. The agarose and boric acid contents were systematically varied between 0.2–1.0% and 320–640 mM, respectively. The influence of several physical parameters such as viscosity and electroosmotic flow were also investigated, the latter to shed light on its effect on the electrokinetic injection bias. Three dimensional Ferguson plots were utilized to better understand the sieving performance of the various agarose/TBE ratio gels, especially relying on their slope (retardation coefficient, KR) value differences. The best resolution between the LC and non-glycosylated HC IgG subunits was obtained by utilizing the molecular sieving effect of the 1% agarose/320 mM boric acid composition (ΔKR = 0.035). On the other hand, the 0.8% agarose/640 mM boric acid gel showed the highest separation power between the similar molecular weight, but different surface charge density non-glycosylated HC and HC fragments (ΔKR = 0.005). It is important to note that the agarose-based gel-buffer systems did not require any capillary regeneration steps between runs other than simple replenishment of the sieving matrix, significantly speeding up analysis cycle time.

МІЖНАРОДНА ЕКОНОМІЧНА ІНТЕГРАЦІЯ ТА ЕКОНОМІЧНА ГЛОБАЛІЗАЦІЯ: СПІЛЬНЕ ТА ВІДМІННЕ

The economic development of the modern world is taking place in the context of globalization, which is characterized by a comprehensive transformation of the world community into an open integrated system of information and communication, technological, financial and economic, political, socio-cultural ties and interactions. This process is confronted with the phenomenon associated with the formation of various types of integration associations. As a result, in the development of international economic integration (IEI) and economic globalization (EG) there are certain contradictions that need to be overcome in the interests of the world community. With this in mind, the aim of the study is to determine the common and distinctive features of IEI and EG. To implement it, the task of identifying the factors of the globalization process has been formulated and implemented; comparison of IEI and EG on certain grounds; characteristics of glocalization as fragmented global economic space, which is formed as a result of the interaction of IEI and EG. In identifying common and distinctive features of IEI and EG, features such as function, trend, process, object of influence and subject of action are used and their different importance in the interaction of these phenomena is proved. Different functions of IEI and EG are indicated. Their different process orientation and even the opposite was proved on the basis of analysis of the latest scientific sources. The tendencies of development of these phenomena are somewhat coincident, as integration as the union of certain parts as a whole confirms the tendency towards integrity, but in local terms. The greatest coincidence between IEI and EG is manifested in the object dimension, which is expressed through the various components of international economic activity. The key role among them belongs to world trade, the dynamics of which is constantly changing under the influence of such objective factors as the international division of labor, fragmentation of global production and value chains, specialization, accelerating foreign movement direct investment and increasing competition. The results of the study confirmed hypothesis about the relationship and at the same time the opposite of IEI and EG, interaction which are inherent the ratio of intersection. The analysis of IEI and EG trends was carried out taking into account the influence of various factors, including of convergent NBICS-technologies. Glocalization, which is a consequence of the interaction of IEI and EG, which is a certain synthesis of global and local, is characterized. In the global segment the boundary current states of IEI and EG intersect. Based on the formulated scientific statements, it is concluded that IEI, EG and glocalization form a fragmented global economic space. The size of this spatial segment and the characteristics are not constant, but depend on which trend ‒ global or local prevails. It is proved that in the future the most popular will be the research related to the systematic analysis of the essence of glocalization.

МІЖНАРОДНІ ЕКОНОМІЧНІ ВІДНОСИНИ ЯК ГЛОБАЛІЗОВАНА СИСТЕМА

Based on a critical analysis of the latest Ukrainian and foreign scientific sources determined the nature and content of IER as a globalized system, identified factors, subjects of managerial influence, mechanisms and tools for regulating IER. The using a systematic approach made it possible to take into account the impact of internationalization, globalization and integration on the formation of a modern system of IER. It was also found that IER are developing under the influence of such internal factors as the intensive development of world trade, foreign direct investment movement, which contribute to the fragmentation of global value chains, deepen specialization and increase competition. Under such conditions, the requirements for the level of regulation of relations between active participants in IER increase. This, in turn, requires to the identification of economic and political interests and motives for management decisions by the main actors in IER, which is possible only on the basis of a systematic view of the structural structure of this social phenomenon. It is proved that the formation of current trends in IER is significantly influenced not only by globalized firms, but also leading countries and international organizations, which shows the unconvincing conclusions of domestic experts on the declining role of national governments as influential economic actors. Leaders of developed countries, as well as the owners of globalized companies, successfully using modern information and communication technologies, international organizations and the system of artificial ratings, make decisions in their favor, carry out global governance in the interests of the «golden billion». Despite the spread of openness and transparency in trade and financial and economic transactions, influential actors in international relations prefer not so much economic as political influence. The scientific novelty and practical value of this research lies in the substantiation of the listed scientific propositions and generalizations. According to its results, the prospects of further scientific research in this area are outlined, which are related to development the effective legal framework for regulating international economic relations in the face of current threats and challenges facing the world community.

Photoprocessing of H2S on dust grains

Context. Sulfur is a biogenic element used as a tracer of the evolution of interstellar clouds to stellar systems. However, most of the expected sulfur in molecular clouds remains undetected. Sulfur disappears from the gas phase in two steps. The first depletion occurs during the translucent phase, reducing the gas-phase sulfur by 7–40 times, while the following freeze-out step occurs in molecular clouds, reducing it by another order of magnitude. This long-standing question awaits an explanation. Aims. The aim of this study is to understand under what form the missing sulfur is hiding in molecular clouds. The possibility that sulfur is depleted onto dust grains is considered. Methods. Experimental simulations mimicking H2S ice UV photoprocessing in molecular clouds were conducted at 8 K under ultra-high vacuum. The ice was subsequently warmed up to room temperature. The ice was monitored using infrared spectroscopy, and the desorbing molecules were measured by quadrupole mass spectrometry in the gas phase. Theoretical Monte Carlo simulations were performed for interpretation of the experimental results and extrapolation to the astrophysical and planetary conditions. Results. H2S2 formation was observed during irradiation at 8 K. Molecules H2Sx with x > 2 were also identified and found to desorb during warm-up, along with S2 to S4 species. Larger Sx molecules up to S8 are refractory at room temperature and remained on the substrate forming a residue. Monte Carlo simulations were able to reproduce the molecules desorbing during warming up, and found that residues are chains of sulfur consisting of 6–7 atoms. Conclusions. Based on the interpretation of the experimental results using our theoretical model, it is proposed that S+ in translucent clouds contributes notoriously to S depletion in denser regions by forming long S chains on dust grains in a few times 104 yr. We suggest that the S2 to S4 molecules observed in comets are not produced by fragmentation of these large chains. Instead, they probably come either from UV photoprocessing of H2S-bearing ice produced in molecular clouds or from short S chains formed during the translucent cloud phase.

C9ORF72 repeat expansion is not associated with atypical parkinsonism in the Serbian population

These include, among others, two forms of atypical Parkinsonism, multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). This study aimed to assess the potential role of C9orf72 repeat expansions among Serbian patients diagnosed with MSA and PSP. Genomic DNA of 44 MSA patients, 73 PSP patients, and 96 controls was extracted from peripheral blood, and normal C9orf72 alleles were analyzed by standard quantitative fluorescence polymerase chain reaction (QF-PCR) and fragment analysis. Subsequently, for all samples presenting a single allele, repeat-primed PCR was performed with two different sets of primers to avoid a false-negative result. Thirty repeats were used as a pathogenic cut-off and 20-29 repeats for the intermediate alleles. No pathological C9orf72 expansions were detected in the MSA and PSP patients nor the control subjects. In the MSA group, the most common was the allele with 2 repeats, and the largest repeat number was 14. Among PSP patients, the most common allele also had 2 repeats, while the largest detected repeat size within the normal range was 17. Also, we identified one PSP patient that had an intermediate size allele (25 repeats). We did not find correlation between the number of repeats and disease onset, age at the time of examination, or disease duration in MSA or PSP patients. Regarding family history, in PSP the sum of both allele repeats numbers was higher in patients with positive family history than in sporadic cases. The results presented in this study are the first systematic assessment of C9orf72 allele sizes among patients diagnosed with MSA and PSP in the Serbian population. Although the potential role of intermediate C9orf72 repeats in neurodegenerative disorders is still to be elucidated, our results support the current knowledge that C9orf72 repeat expansions are not associated with MSA and PSP.

Production of vector mesons in the string+P30 model of polarized quark fragmentation

The production of vector mesons in the fragmentation process of polarized quarks is studied within the recursive String+${}^3P_0$ model, improving a previous version of the model in which the production of pseudoscalar mesons only was considered. Two types of couplings of the vector meson to quarks are introduced, their coupling constants being the additional free parameters of the model. The angular distribution of the decay products of the polarized vector meson is deduced from the spin density matrix of the meson and the spin information is propagated along the fragmentation chain taking into account the entanglement of spin states. The new model is implemented in a stand alone Monte Carlo program utilized to investigate in detail kinematic distributions and transverse spin asymmetries. The sensitivity of these observables to the new free parameters is discussed and the Monte Carlo results are compared with experimental data on transverse spin asymmetries.

Processing trade in Chinese interregional input–output tables: construction and application

We construct new interregional input–output tables for China, which can be used to analyze changes in the interindustry linkages within and between eight Chinese regions, and their consequences. We claim that analyses based on these tables yield more accurate results than analyses using existing interregional input–output tables for China, because our tables explicitly account for a typical feature of the Chinse economy: the importance of processing exports activities. These activities rely heavily on imported inputs and much less on inputs sourced from domestic regions. Accounting for such differences between processing exports and other production activities reduces aggregation biases. We illustrate the usefulness of the tables by computing supply chain fragmentation indices for China and quantifying the biases that are avoided by using our input–output tables instead of conventional ones. We make our tables (for 2002, 2007 and 2012) publicly available.

Structural arrangement of the VH and VL domains in the COBRA™ T-cell engaging single-chain diabody.

COBRA™ (COnditional Bispecific Redirected Activation) T-cell engagers are designed to target solid tumors as a single polypeptide chain prodrug that becomes activated by proteolysis in the tumor microenvironment. One COBRA molecule comprises seven Ig domains: three single-domain antibodies (sdAbs) recognizing a tumor target or human serum albumin (HSA), and CD3ε-binding variable fragment heavy chain (VH) and variable fragment light chain (VL) and their inactivated counterparts, VHi and VLi. Pairing of VH and VL, and VLi and VHi into single-chain variable fragments (Fv) is prevented by shortened inter-domain linkers. Instead, VH and VL are expected to interact with VLi and VHi, respectively, thus making a diabody whose binding to CD3ε on the T-cells is impaired. We analyzed the structure of an epidermal growth factor receptor (EGFR) COBRA in solution using negative stain electron microscopy (EM) and small-angle X-ray scattering (SAXS). We found that this EGFR COBRA forms stable monomers with a very dynamic interdomain arrangement. At most, only five domains at a time appeared ordered, and only one VH-VL pair was found in the Fv orientation. Nonenzymatic posttranslational modifications suggest that the CDR3 loops in the VL-VHi pair are exposed but are buried in the VH-VLi pair. The MMP9 cleavage rate of the prodrug when bound to recombinant EGFR or HSA is not affected, indicating positioning of the MMP9-cleavable linker away from the EGFR and HSA binding sites. Here, we propose a model for EGFR COBRA where VH and VLi form an Fv, and VL and VHi do not, possibly interacting with other Ig domains. SAXS and MMP9 cleavage analyses suggest that all COBRA molecules tested have a similar structural architecture.

RHEOKINETIC AND MORPHOLOGICAL FEATURES OF THE REACTION FORMATION OF A POLYMER COMPOSITE MATERIAL BASED ON IMPACT-RESISTANT POLY(METHYL METHACRYLATE). MODEL AND APPLIED ASPECTS

Based on the experimental data on the rheology of dispersions of hydrophobic aerosil (Am) in a low molecular weight hydrocarbon medium, the possibility of using a «micellar» mechanism for the formation of a bulk structure for such dispersions is considered. A model of such a structure before, during and after shear deformation is proposed, which makes it possible to interpret experimental data on the rheology of dispersed systems. The results of the study of rheokinetics are presented in a new visio – from the point of view of self-organization under the influence of the shear field. The PMMA–PU–Am system was considered as a polymer composite (PC), in which the matrix is the poly(methyl methacrylate) (PMMA) being modified, and the dispersed phase is a mixture of polyurethane (PU) with Am. It has been shown that during the reaction formation of this composition, the conditions of shear deformation of the system correspond to those at which self-organization and fixation of the coagulation rheopex structure of the nanofiller in PC is possible at the moment of reaching very high viscosity values (gel-point), when diffusion processes will be practically frozen. Two concentration regions of Am were predicted (before and after the percolation threshold), where an enhancement of the mechanical characteristics of PMMA can be expected. The relationship between the rheokinetics of the formation of a linear PMMA–crosslinked PU mixture in the presence of different amounts of oligomeric azo-initiator containing fragments of the polyurethane chain and groups capable of initiating radical polymerization of methyl methacrylate and the process of phase separation, morphology and mechanical properties of the final products has been established. It was shown that the time of phase separation and gelation are interrelated and there is in a simple dependence on the concentration of the azo-initiator. Such an initiator affects the structural-rheological transitions in the system and leads to the formation of morphology with smaller domains. The most stable system with the best dispersion of polyurethane in polymethyl methacrylate is a mixture containing 0.002 mol/L of azo-initiator, which has improved mechanical properties and increased impact viscosity.

StringSpinner - adding spin to the PYTHIA string fragmentation

StringSpinner is a plugin allowing for the introduction of spin effects in the hadronization part of the PYTHIA 8 event generator. In this first version the implementation is limited to handling pesudoscalar mesons in events without parton showers. The spin effects are generated by propagating the quark polarization along the fragmentation chain according to the rules of the quantum mechanical string+P03 model. By using parametrizations for the transversity parton distribution functions, StringSpinner allows to simulate the polarized semi inclusive deep inelastic scattering process on protons and neutrons. The instructions to use StringSpinner and to modify the parametrizations of the transversity distribution functions are presented, as well as an example of the calculation of the Collins asymmetries as obtained from simulations of the transversely polarized semi inclusive deep inelastic scattering process. Program summaryProgram Title: StringSpinnerCPC Library link to program files:https://doi.org/10.17632/37jrpmyz3t.1Developer's repository link:https://gitlab.com/albikerbizi/stringspinner.gitLicensing provisions: GNU GPL v2 or laterProgramming language: C++, FortranNature of problem: To analyse and interpret the experimental data on the study of the nucleon spin structure, as well as to make predictions for future experiments simulations are needed.Solution method: Introduce spin effects in the hadronization part of a complete Monte Carlo event generator, largely used in the community of high energy particle physicists.

Kapitza resistance at a domain boundary in linear and nonlinear chains.

We explore Kapitza thermal resistance on the boundary between two homogeneous chain fragments with different characteristics. For a linear model, an exact expression for the resistance is derived. In the generic case of frequency mismatch between the domains, the Kapitza resistance is well defined in the thermodynamic limit. At the same time, in the linear chain, the resistance depends on the thermostat properties and therefore is not a local property of the considered domain boundary. Moreover, if the temperature difference at the ends of the chain is fixed, then neither the temperature drop at the domain boundary nor the heat flux depend on the system size; for the normal transport, one expects the scaling N^{-1} for both. For specific assessment, we consider the case of an isotopic boundary-only the masses in different domains are different. If the domains are nonlinear, but integrable (Toda lattice, elastically colliding particles), the anomalies are similar to the case of linear chain, with the addition of well-articulated thermal dependence of the resistance. For the case of elastically colliding particles, this dependence follows a simple scaling law R_{k}∼T^{-1/2}. For Fermi-Pasta-Ulam domains, both the temperature drop and the heat flux decrease with the chain length, but with different exponents, so the resistance vanishes in the thermodynamic limit. For the domains comprised of rotators, the thermal resistance exhibits the expected normal behavior.

Shelf-Life Extension of Fc-Fused Single Chain Fragment Variable Antibodies by Lyophilization.

Generation of sequence defined antibodies from universal libraries by phage display has been established over the past three decades as a robust method to cope with the increasing market demand in therapy, diagnostics and research. For applications requiring the bivalent antigen binding and an Fc part for detection, phage display generated single chain Fv (scFv) antibody fragments can rapidly be genetically fused to the Fc moiety of an IgG for the production in eukaryotic cells of antibodies with IgG-like properties. In contrast to conversion of scFv into IgG format, the conversion to scFv-Fc requires only a single cloning step, and provides significantly higher yields in transient cell culture production than IgG. ScFv-Fcs can be effective as neutralizing antibodies in vivo against a panel of pathogens and toxins. However, different scFv fragments are more heterologous in respect of stability than Fab fragments. While some scFv fragments can be made extremely stable, this may change due to few mutations, and is not predictable from the sequence of a newly selected antibody. To mitigate the necessity to assess the stability for every scFv-Fc antibody, we developed a generic lyophilization protocol to improve their shelf life. We compared long-term stability and binding activity of phage display-derived antibodies in the scFv-Fc and IgG format, either stored in liquid or lyophilized state. Conversion of scFv-Fcs into the full IgG format reduced protein degradation and aggregation, but in some cases compromised binding activity. Comparably to IgG conversion, lyophilization of scFv-Fc resulted in the preservation of the antibodies’ initial properties after storage, without any drop in affinity for any of the tested antibody clones.

Taxonomy of Mitochondrial Cytochrome B Proteins of the Same Amino Acid Sequence Length.

Prior to this study, we discovered a protein characterized by many different amino acid sequences with the same number of amino acid residues. This turned out to be a unique cytochrome b, in which 1048 molecules out of 1689 contain 379 amino acid residues. A detailed study of the occurrence of this protein in living organisms at different taxonomic levels (from biological domains to biological orders of animals) has been carried out in the work presented here. We found that the main part of all b cytochromes is present in eukaryotes (99.2%), in biological kingdoms (95.9% in animals), in biological phylums (97.5% in chordates), and in biological classes (79.7% in mammals). Withal, this protein, containing 379 amino acid residues and characterized by many different amino acid sequences, is found only in eukaryotes (100%), only in animals (100%) and mainly in mammals (81.1%). Thus, a representative that has cytochrome b with a corresponding number of amino acid residues has not yet been identified among archaea and prokaryotes, while it is common in representatives of different biological types, classes, and orders of animals. It is believed that the structural diversity of a given protein within the same length and its one function of participation in the process of electron transfer relate to the physicochemical features of the extra- and intramembrane fragments of the polypeptide chain of this protein.

Dissection of the amyloid formation pathway in AL amyloidosis

In antibody light chain (AL) amyloidosis, overproduced light chain (LC) fragments accumulate as fibrils in organs and tissues of patients. In vitro, AL fibril formation is a slow process, characterized by a pronounced lag phase. The events occurring during this lag phase are largely unknown. We have dissected the lag phase of a patient-derived LC truncation and identified structural transitions that precede fibril formation. The process starts with partial unfolding of the VL domain and the formation of small amounts of dimers. This is a prerequisite for the formation of an ensemble of oligomers, which are the precursors of fibrils. During oligomerization, the hydrophobic core of the LC domain rearranges which leads to changes in solvent accessibility and rigidity. Structural transitions from an anti-parallel to a parallel β-sheet secondary structure occur in the oligomers prior to amyloid formation. Together, our results reveal a rate-limiting multi-step mechanism of structural transitions prior to fibril formation in AL amyloidosis, which offers, in the long run, opportunities for therapeutic intervention.

The Characteristics of Regional Value Chains in the Sector of Chemicals and Pharmaceutical Products in the EU

The COVID-19 pandemic has impacted trade flows, causing a trade drop in 2020 that was especially sensitive for pharmaceutical and medical products necessary to ensure public health. The production of pharmaceutical products is dispersed in a framework of global value chains. This study aimed to provide a detailed analysis of the EU situation in the sector of production of chemical and pharmaceutical products, to discover the fragmentation of production chains within the EU as well as globally. International inter-country input–output tables were employed to disaggregate the value-added created in EU member states. The GVC and RVC participation indexes, backward and forward participation, length of sourcing, and selling value chains were calculated and compared with the main global hubs.

Sustainability supplier scorecard assessment tools: A comparison between apparel retailers

ABSTRACT The purpose of this qualitative study is to evaluate and compare eight sustainability supplier scorecard assessment tools in use among five major international apparel retailers, Walmart, Eileen Fisher, Nike, H&M, and Gap. Inductive content analysis was used to study the raw textual data and make evidence-based inferences. Results showed that the field of sustainable supply chain management (SSCM) is subject to inefficiencies because there are inadequate standards for reporting information which would expose these inefficiencies. The investigated tools varied in terms of scope, performance measurements, and scoring methodologies, which had negative effects on their comparability. This obstacle, however, does not invalidate the major findings, which revealed an evident and concerning lack of information to support the practical application of the tools investigated. Because no retailer disclosed information about its lower tier suppliers’ assessments, it is uncertain whether and how suppliers in lower tiers are engaged in sustainability assessments. Because sustainability violations occur at a higher rate within fragmented supply chains, it is critical to communicate supplier engagement throughout the value chain. The findings of this study urge the application of standardized and comprehensive scorecard assessments which would help to enhance the credibility of SSCM practice, its assessment, and its communication.

Novel Plantibodies Show Promise to Protect Citrus from Greening Disease

Candidatus Liberibacter asiaticus (CLas), the bacteria responsible for citrus greening disease [huanglongbing (HLB)], has become a worldwide threat to citrus (Citrus sp.) production. HLB has proven difficult to study and treat because of the complex interactions between CLas, the citrus host, and insect vectors. We have selected for single chain fragment variable (scFv) antibodies from a specialized bacteriophage library for binding activity against CLas proteins InvA and TolC. Portions of each protein were chosen as antigens based on predicted binding availability and theorized necessary functions in pathogenicity. Binding affinity for individual scFv-expressing clones was confirmed by phage enzyme-linked immunosorbent assay (ELISA). The scFv sequences were stably transformed under the control of a tandem Cauliflower mosaic virus 35S (CaMV 2x35S) promoter by Agrobacterium tumefacien–mediated transformation into ‘Carrizo’ citrange (Citrus sinensis × Poncirus trifoliate), a citrus rootstock cultivar. Replicated plants of single transformations were inoculated by infestation with CLas positive asian citrus psyllid (Diaphorina citri), a CLas vector. Inoculation and disease progression was monitored through quantitative real-time polymerase chain reaction. Inoculated transgenic plants showed significantly reduced CLas titer compared with wild types. A subpopulation of transgenic plants displayed no measurable surviving bacteria after 12 months. Interestingly, individual replicated plants from the same transgenic events strongly segregated into two populations by resistance phenotype: a minority that were indistinguishable from wild-type plants and a majority that were highly resistant. Our results are the first step in developing a novel protection strategy for HLB.