Mechanism and origin of enantioselectivity for organocatalyzed asymmetric heteroannulation of alkynes in the construction of axially chiral C2-arylquinoline.

Axially chiral C2-arylquinoline has been successfully constructed via asymmetric heteroannulation of alkynes catalyzed by chiral phosphoric acid with high yield and high enantioselectivity. Inspired by this intriguing work, theoretical calculations have been carried out, and the detailed reaction mechanism has been elaborated, in which the whole reaction can be divided into steps including hydrogen transfer, C-N bonding, annulation reaction and the final dehydration processes. The initial hydrogen-transfer reaction has two possible pathways, while the subsequent C-N bonding process has eight possible pathways. Then, after the annulation reaction and the final dehydration processes, the major product and byproduct were formed. QTAIM and IGMH analyses were used to illustrate the role of weak intermolecular interactions in the catalytic process, and the distortion/interaction and EDA analyses provided a deeper understanding of the origin of enantioselectivity. The calculated results are consistent with the experimental results. This work would provide valuable insights into asymmetric reactions catalyzed by chiral phosphoric acid.

Investigations of the reaction mechanism of sodium with hydrogen fluoride to form sodium fluoride and the adsorption of hydrogen fluoride on sodium fluoride monomer and tetramer.

CONTEXT: The reaction between Na and HF is a typical harpooning reaction which is of great interest due to its significance in understanding the elementary chemical reaction kinetics. This work aims to investigate the detailed reaction mechanisms of sodium with hydrogen fluoride and the adsorption of HF on the resultant NaF as well as the (NaF)4 tetramer. The results suggest that the reaction between Na and HF leads to the formation of sodium fluoride salt NaF and hydrogen gas. Na interacts with HF to form a complex HF···Na, and then the approaching of F atom of HF to Na results in a transition state H···F···Na. Accompanied by the broken of H-F bond, the bond forms between F and Na atoms as NaF, then the product NaF is yielded due to the removal of H atom. The resultant NaF can further form (NaF)4 tetramer. The interaction of NaF with HF leads to the complex NaF···HF; the form I as well as II of (NaF)4 can interact with HF to produce two complexes (i.e., (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF), but the form III of (NaF)4 can interact with HF to produce only one complex (NaF)4(III)···HF. These complexes were explored in terms of noncovalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analyses. NCI analyses confirm the existences of attractive interactions in the complexes HF···Na, NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF. QTAIM analyses suggest that the F···Na interaction forms in the HF···Na complex while the F···H hydrogen bonds form in NaF···HF, (NaF)4(I-1)···HF, (NaF)4(I-2)···HF, (NaF)4(II-1)···HF and (NaF)4(II-2)···HF, and (NaF)4(III)···HF complexes. Natural bond orbital (NBO) analyses were also applied to analyze the intermolecular donor-acceptor orbital interactions in these complexes. These results would provide valuable insight into the chemical reaction of Na and HF and the adsorption interaction between sodium fluoride salt and HF. METHODS: The calculations were carried out at the M06-L/6-311++G(2d,2p) level of theory which were performed using the Gaussian16 program. Intrinsic reaction coordinate (IRC) calculations were carried out at the same level of theory to confirm that the obtained transition state was true. The molecular surface electrostatic potential (MSEP) was employed to understand how the complex forms. Quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) analysis was used to know the topology parameters at bond critical points (BCPs) and intermolecular interactions in the complex and intermediate. The topology parameters and the BCP plots were obtained by the Multiwfn software.

Maintenance of cell integrity during hydroxyl radical rapid inactivation of Pseudanabaena sp. and simultaneous mineralization of odor compound 2-methylisoborneol.

Pseudanabaena sp. and the odor compound it produces, 2-methylisoborneol (2-MIB), has been reportedly responsible for off-flavor pollution worldwide, leading to substandard drinking water sensory indicators and serious water supply crises. In this paper, the hydroxyl radical (•OH) produced by the synergistic effect of strong ionization discharge and hydrodynamic cavitation rapidly inactivated Pseudanabaena sp. and simultaneously mineralized 2-MIB to a concentration of 2.57 ng/L, which is below the odor threshold of 10 ng/L for a total reactive oxidants (TRO) concentration of 1.2 mg/L within 12 s. Crucially, the intracellular 2-MIB level was maintained in approximately 155.26- 162.29 ng/L range, indicating that 2-MIB was not released from the cells. Based on the scanning electron microscopy (SEM) results, the integrity of Pseudanabaena sp. cells was maintained with intact membranes and no intracellular organic matters (IOM) released during •OH inactivation. In contrast, ClO2 caused severe membrane rupture and massive IOM release. Based on the gas chromatograph/mass spectrometer (GC/MS) analyses and mass spectral database, the chromatogram fitted the baseline with a TRO concentration of 4 mg/L and no peaks corresponding to intermediates were detected. Moreover, •OH could mineralize 2-MIB by opening the ring structures of 1,2,3,3-tetramethyl-4-cyclopentenone, neomenthol, and 2-methylcyclohexene-1-aldehyde to produce small-molecule compounds, finally leading to CO2 and H2O formation via three reaction pathways. Therefore, the •OH not only maintained the cell integrity of Pseudanabaena sp. during inactivation but also mineralized 2-MIB simultaneously.

Klebsiella michiganensis: a nitrogen-fixing endohyphal bacterium from Ustilago maydis.

Ustilago maydis is a pathogenic fungus in Basidiomycota causing corn smut disease. A strain of U. maydis YZZF202006 was isolated from the tumor of corn smut collected from Jingzhou city in China. The intracellular bacteria were confirmed inner hyphal of the strain YZZF202006 by PCR amplification and fluorescence in situ hybridization (FISH) and SYTO-9. An endohyphal bacterium YZUMF202001 was isolated from the protoplasts of the strain YZZF202006. It was gram-negative, short rod-shaped with smooth light yellow colony. The endohyphal bacterium was genomic evidenced as Klebsiella michiganensis on the basis of average nucleotide identity (ANI) analysis and the phylogram. Then K. michiganensis was GFP-Labeled and reintroduced into U. maydis, which confirmed the bacterium can live in hyphae of U.maydis. The bacterium can grow on N-free culture media. Its nitrogenase activity was reached av. 646.25 ± 38.61 nmol·mL- 1·h- 1 C2H4 by acetylene reduction assay. A cluster of nitrogen fixation genes (nifJHDKTXENXUSVWZMFLABQ) was found from its genome. The endohyphal K. michiganensis may play an important role to help nitrogen fixation for fungi in the future.

AIE Ligand-Based Luminescent Ln-MOFs for Rapid and Selective Sensing of Tetracycline.

The design of highly stable and dual-emission lanthanide metal-organic frameworks (Ln-MOFs) is promising for practical chemical sensor applications. Rational design and synthesis of photoresponsive organic ligands provide a feasible approach to achieving highly fluorescent dual-emission Ln-MOFs. In this study, a tetraphenylpyrazine-based AIE ligand, H4L, was synthesized and combined with lanthanide ions (including Sm3+, Eu3+, Gd3+, and Tb3+) to fabricate a series of Ln-MOFs named Ln-L. The single-crystal analysis revealed that all Ln-L belonged to the tetragonal space group P4212 and featured a 2-fold interpenetrated 3D structure. Leveraging rational design, Eu-L exhibited a sensitive response to tetracycline, making it a promising fluorescence sensor for tetracycline detection. The experiments demonstrated that Eu-L could rapidly and quantitatively detect tetracycline and its analogs within 30 s. The lowest detection limits for tetracycline, oxytetracycline, and chlortetracycline were 0.43, 0.92, and 0.81 µM, respectively. Additionally, the probe displayed excellent reusability and exceptional selectivity. A plausible sensing mechanism was proposed, supported by both experimental and theoretical analyses. Furthermore, the study discovered that on-site and real-time determination of TCs in aqueous solutions could be achieved by using luminescence test papers and composite films derived from Eu-L.

Solvatomorphism and first-time observation of acid-acid catemer in 4-phenylamino-benzoic acids.

To investigate the polymorphism in 4-phenylamino-benzoic acids (4-PABAs) in general, and the effect on the polymorphism of these compounds exerted by substitution in particular, a series of 4-PABAs (1-8) varying in the substitution position and pattern were synthesized, and their polymorphic behavior was investigated for the first time. A relatively comprehensive polymorph screening led to the discovery of two forms, one solvent-free and the other solvate, for compounds 1, 3 and 8, and one form for the other compounds. The crystal structures were determined by single-crystal XRD. All the 4-PABAs in the crystal structures are highly twisted, and all the solvent-free crystals are based on the conventional acid-acid dimer motif, except for 2, which has a rarely observed acid-acid catemer motif. Two of the solvates (1-S and 8-S) have pyridine in the lattice while the other (3-S) has dichloromethane. The observation indicates that neither conformational flexibility or substitution alone nor the combination of both leads to polymorphism in these compounds, which is in dramatic contrast to the polymorphism of fenamic acids. The thermal properties of each system were investigated by differential scanning calorimetry and desolvation of the solvates was studied by thermogravimetric analysis. Hirshfeld surface analysis and molecular dynamics simulation were performed to study the mechanism of polymorphism and the intermolecular interactions contributing to the formation and stability of each crystal form.

Aryl-to-Vinyl 1,4-Nickel Migration/Reductive Cross-Coupling Reaction for the Stereoselective Synthesis of Multisubstituted Olefins.

The aryl-to-vinyl nickel 1,4-migration (1,4-Ni migration) reaction has been reported for the first time. The generated alkenyl Ni species undergo a reductive coupling reaction with unactivated brominated alkanes affording a series of trisubstituted olefins. This tandem reaction exhibits mild conditions, a broad substrate scope, high regioselectivity, and excellent Z/E stereoselectivity. A series of controlled experiments have shown that the critical 1,4-Ni migration process is reversible. In addition, the alkenyl nickel intermediates obtained after migration are highly Z/E stereoselective and do not undergo Z/E isomerization. The obtained trace isomerization products are caused by the instability of the product.

Visible-Light-Driven [3 + 2]/[4 + 2] Annulation Reactions of Alkenes with N-Aminopyridinium Salts.

The annulation reactions of benzoamidyl radicals with alkenes were realized under visible light irradiation with fac-Ir(ppy)3 as catalyst and N-aminopyridinium salts as benzoamidyl radical precursors. The reaction can deliver two distinct types of products: in the case of vinyl arenes, [3 + 2] annulation product dihydrooxazoles were yielded exclusively; when alkyl-substituted alkenes were used, on the other hand, it afforded [4 + 2] annulation product dihydroisoquinolinones. Factors determining the reaction consequence were elucidated by DFT calculations.

First Report of stem rot in Cymbidium sinense Caused by Fusarium oxysporum (FOSC) in China.

Cymbidium sinense (Jackson ex Andr.) Willd is a perennial terrestrial plant in the orchid family mainly distributed in China, Japan, India and Southeast Asia that occupies a strong position in the flower market due to its bright green leaves and fragrant flowers (Zhang et al. 2013). Cymbidium sinense is not only valued by people for its ornamental and economic value, but its roots have antiasthmatic medicinal properties (Ke et al. 2004). In August 2020, about 15% stem rot on two-year old C. sinense with varying severity was observed in five nursery gardens located in Enshi city (N 30° 16', E 109° 29'), Hubei province, China. Typical symptoms of C. sinense included roots and inner part of the pseudobulbs changing from white to brown and rotting. Leaves became brown and withered from bottom to top, and there was an obvious blight yellow halo at the junction of diseased and healthy tissue, which eventually caused the whole plant to wilt and die (Fig. 1d). To isolate the pathogen, a total of 15 leaf tissues from the disease-health junction (3 × 3 mm) from 5 individual plants (3 leaves/plant) with symptoms were surface sterilized with 75% ethanol for 30 s and 2% sodium hypochlorite (NaOCl) for 3 min. The sterilized tissue was rinsed three times with sterilized water, and then placed on potato dextrose agar (PDA) for incubation at 28°C in the dark for 5 days. Isolated colonies were subcultured by a hyphal tip protocol. Thirteen fungal isolates were obtained. Through preliminary pathogenicity tests, we found that ten isolates induced leaf blight. These ten isolates with pathogenicity showed similar morphological characteristics, with initial white-flocculent aerial mycelium that secreted a lavender pigment and produced colonies with an irregular edge after 3 days on PDA. The ten strains were cultured on PDA plates at 28℃ for 5 and 15 days to observe colony and conidial characteristics. The ten strains were identified as Fusarium based on morphological characteristics (Leslie and Summerell 2006). Strain ML0303 was selected for further identification. Macroconidia were falciform, hyaline, slightly pointed at both ends with two to four septa, 24.0 ± 5.6 µm × 4.7 ± 0.8 µm (n = 50). Microconidia were hyaline, oval, globose, with zero to one septum, 5.5 ± 1.3 µm × 2.2 ± 0.5 µm (n = 50) (Fig. 1c). Total genomic DNA of strain ML0303 was extracted with a CTAB protocol (Stenglein and Balatti 2006). The translation elongation factor (EF-1α), RNA polymerase II second largest subunit (RPB2) and ß-tubulin (Tub2) genes were amplified respectively using primer pairs EF1/EF2, RPB2-5F2/RPB2-7cR and T1/T22 respectively (O'Donnell. et al. 2010, O'Donnell. et al. 1997). The EF-1α, RPB2 and Tub2 (accession numbers-MW719874, OL614838, OL689398, respectively) gene sequences were submitted to GenBank. EF-1α, RPB2 and Tub2 sequences of ML0303 showed 99.5% - 100% identity respectively with Fusarium oxysporum in the Genbank and FUSARIUM-ID databases. The multilocus sequence data was used to infer a phylogenetic tree via a Neighbor-joining (NJ), Maximum-likelihood (ML) and Maximum-Parsimony(MP) together with reference sequences from GenBank. The topology of the three trees was similar; only the NJ tree is presented here. Strain ML0303 and F. oxysporum formed a clade supported with high values (NJ/ML/MP: 96,95,97). The results indicated that the fungus was F. oxysporum based on the phylogenetic analysis and BLASTn queries. For pathogenicity tests, conidia of strain ML0303 were collected by rinsing PDA plates. Two-year-old C. sinense grown in plastic pots filled with sterilized autoclaved sandy loam soil were used for the tests. Three pots (two plants/pot) were included in each treatment. Spore suspensions (106spores/ml) of strain ML0303 were used to irrigate the stem-zone of the plants, and sterile water was used as control. The two treatments were placed in a greenhouse and incubated at 28±2℃ with a 14-hour light/10-hour dark cycle. The experiment was repeated twice. After three weeks, stem rot symptoms were observed on C. sinense inoculated with ML0303, that were the as same as observed in the nursery (Fig. 1e-h). No symptoms were observed on the negative control. Fusarium oxysporum was re-isolated from the infected plants to fulfill Koch's postulates. Partial EF-1α and RPB2 gene sequences were used for molecular identification. Members of the FOSC are notorious for causing many diseases, which includes stem rot of Sulcorebutia heliosa and root rot of Torreya grandis (Garibaldi et al. 2020; Zhang et al. 2016). To our knowledge, this is the first report of stem rot by F. oxysporum on C. sinense in China. The finding of this pathogen provides a clear target for stem rot control.

Plant Growth-Promoting Ability of Mycorrhizal Fusarium Strain KB-3 Enhanced by Its IAA Producing Endohyphal Bacterium, Klebsiella aerogenes.

Fusarium oxysporum KB-3 had been reported as a mycorrhizal fungus of Bletilla striata, which can promote the seed germination and vegetative growth. Endohyphal bacteria were demonstrated in the hyphae of the KB-3 by 16S rDNA PCR amplification and SYTO-9 fluorescent nucleic acid staining. A strain Klebsiella aerogenes KE-1 was isolated and identified based on the multilocus sequence analysis. The endohyphal bacterium was successfully removed from the wild strain KB-3 (KB-3-), and GFP-labeled KE-1 was also transferred to the cured strain KB-3- (KB-3+). The production of indole-3-acetic acid (IAA) in the culturing broths of strains of KE-1, KB-3, KB-3-, and KB-3+ was examined by HPLC. Their IAA productions were estimated using Salkowski colorimetric technique. The highest concentrations of IAA were 76.9 (at 48 h after inoculation), 31.4, 9.6, and 19.4 µg/ml (at 60 h after inoculation), respectively. Similarly, the three fungal cultural broths exhibited plant promoting abilities on the tomato root and stem growth. The results indicated that the ability of mycorrhizal Fusarium strain KB-3 to promote plant growth was enhanced because its endohyphal bacterium, Klebsiella aerogenes KE-1, produced a certain amount of IAA.

First Report of Anthracnose on Rubus rosaefolius Smith Caused by Colletotrichum boninense in China.

Raspberry (Rubus rosaefolius Smith), also called march bubble or milk bubble, is widely distributed and economically important in China. Raspberries are rich in nutrients such as essential amino acids, vitamin C, dietary fiber, superoxide dismutase (SOD) and minerals (Yang et al. 2019). In May 2019, a leaf spot disease was observed on raspberry in Enshi (N29°07'10', E108°23'12'), Hubei province of China. The symptoms were small dark-brown spots (Fig.1) on over 90% of observed plants. To isolate the pathogen, leaf sections (5 mm × 3 mm) from the border of the symptomatic tissue were cut and sterilized with 75% ethanol for 30 s, followed by 2% sodium hypochlorite (NaClO) for 2 min, and then rinsed three times with sterile water. Leaf sections were placed on potato dextrose agar (PDA) medium amended with 25 µg / ml ampicillin and incubated at 25 °C in the dark for 3 days. Isolated colonies were sub-cultured on PDA by hyphal tip transfer. Eight fungal isolates with similar morphology, abundant white aerial hyphae, were collected. Colonies on PDA grew up to 80 mm in diameter by 7 days at 25 °C. The center of each colony became black (Fig.2). Conidia were unicellular, oval and hyaline. Conidia ranged in size from 14.5 to 19.75 µm × 5.80 to 10.20 µm (n=50) in 20% (v/v) V8 vegetable juice medium. No appressoria were observed. Morphological characteristics are similar to those of Colletotrichum spp. (Moriwaki et al. 2003). Total genomic DNA of a representative isolate S1 was extracted with a CTAB method (Stenglein et al. 2006). Internal transcribed spacer (ITS) region of rDNA, actin (ACT) , beta-tubulin (TUB2) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were amplified and sequenced with the primer pairs of ITS4 / ITS5, ACT512F / ACT783R, Bt-2a / Bt-2b and GDF1 / GDR1, respectively (Weir et al. 2012). BLAST results showed that ITS, ACT, TUB2 and GAPDH gene sequences (GenBank accession nos. MN498030, MT780498, MT780496 and MT780497, respectively) were 99% identical to those of Colletotrichum boninense Moriwaki, Sato & Tsukiboshi (GenBank accession nos. MF076598, JX009583, JQ005588 and JX009905, respectively). Concatenated sequences of the four genes were used to conduct a phylogenetic analysis using neighbor-joining method in MEGA7 (Toussaint et al. 2016). The isolate S1 clustered with above C. boninense strains retrieved from NCBI database. Therefore, the present isolate S1 was identified as C. boninense. Pathogenicity tests were performed using one-month-old raspberry plants, 24 controls and 30 inoculated. The plants were sprayed with conidial suspension ( 106 conidia / mL) cultured on 20% (v/v) V8 vegetable juice medium for 15 days. The control plants were sprayed with sterile distilled water. All plants were covered with plastic bags 24h to maintain the relative humidity in the field. Fifteen days after inoculation, typical symptoms of brown spots were observed on leaves similar to the disease on field plants, while the leaves from the control group remained asymptomatic. C. boninense was reisolated and identified from inoculated symptomatic leaves. Anthracnose on raspberry caused by Colletotrichum gloeosporioides (Dai et al. 2013) and C. fioriniae (Schoeneberg et al. 2020) has previously been reported. However, to the best of our knowledge, this is the first report of Colletotrichum boninense causing leaf spot on Raspberry in China. If more reports of this pathogen are found on raspberries, then it may be necessary to develop effective management strategies for controlling this disease.

First Report of Leaf Spot on Akebia trifoliata Caused by Phytophthora nicotianae in China.

Akebia trifoliata (Thunb.) Koidz. is a species in the family Lardizabalaceae, which belongs to deciduous woody lianas. It is an important species of plant used in Chinese medicine. In July 2019, a leaf spot disease was observed on A. trifoliata in a nursery garden in Jingzhou (N 30° 21', E 112° 19'), Hubei Province, China. Symptoms initially appeared as small brown spots and subsequently developed into subcircular or irregular-shaped brown necrotic lesions. In severe cases, the leaves became completely necrotic and abscised. The incidence of leaf symptoms on affected plants ranged was between 30% and 40%. To isolate the pathogen, pieces of symptomatic leaves were collected and excised at the margins of lesions, surface disinfected with 70% ethanol and 0.1% HgCl2, rinsed three times with sterile water, placed on potato dextrose agar (PDA) amended with 50 µg/ml kanamycin, and incubated at 28°C in the dark for 3 days. Isolated colonies were subcultured by transferring hyphal tips. Six fungal isolates were isolated from the collected tissues. All six isolates had similar colony morphologies on on PDA and were composed of white flocculent aerial hyphae. The average radial growth rate of colonies after 7 days was 11.2 mm/d. Isolates were later cultured on 20% V8 juice agar for 20 days to encourage sporulation. Sporangia were produced on V8 media and were colorless, inverted, pear-shaped, and terminal, with obvious mastoid, 22 to 34 × 28 to 46µm (n=50); Oospores were light brown, and suborbicular, with thick wall, 18 to 26µm (n=20); Globose chlamydospores were light brown, and suborbicular, 12 to 32µm (n=50). Antheridia were not observed suggesting homothallism. These morphological charactertistics were identical to those reported for Phytophthora nicotianae (Erwin and Ribeiro 1996). We selected a single isolate 'B2', for molecular identification because it was the most aggressive in leaf pathogenicity assays. The internal transcribed spacer (ITS) region of rDNA was amplified and sequenced using primers ITS1/ITS4 (White et al. 1990). BLAST analyis revealed that the ITS sequence (GenBank accession nos. MT472132) was 100% identical to other P. nicotianae strains (GenBank accession nos. KJ754387). To fulfill Koch's postulates, a 50 ml zoospores suspension (106 spores/ml) of B2 was sprayed on the foliage of three 1-year-old healthy seedlings. Sterile distilled water to inoculate control plants. After 10 days, typical symptoms of dark brown spots were observed on all the inoculated leaves, while the control leaves remained asymptomatic. P. nicotianae was re-isolated from the inoculated, symptomatic leaves, thus confirming Koch's hypothesis. The experiment was repeated three times. To the best of our knowledge, this is the first report of P. nicotianae causing leaf spot on A. trifoliata in China. P. nicotianae is a common stramenopile pathogen that infects many plant hosts. The presence of this pathogen in an A. trifoliata nursery should be carefully considered to mitigate possible outbreaks of this disease in other fields in this growing region.

Study on molecular mechanisms of nattokinase in pharmacological action based on label-free liquid chromatography-tandem mass spectrometry.

Cardiovascular diseases (CVDs) are the leading causes of premature death and disability in people around the world. Therefore, the prevention and treatment of CVDs has become an important subject. In this study, we verified the thrombolytic activities of a nattokinase-like protease named NK-01 in vivo. Label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique was used in our study. NK-01 could inhibit the activity of coagulation factors though the up-regulation of proteinase C inhibitors and protein S. NK-01 also could inhibit the angiotensinogen conversion to AngII and promote the degradation of kininogen to reduce the blood pressure. In addition, NK-01 could increase the content of paraoxonase 1, which could prevent atherosclerosis. In our study, we found that NK-01 cloud effect some key proteins which participant in CVDs associated metabolic processes such as coagulation system, blood pressure, and atherosclerosis. Taken together, the underlying molecular mechanisms for the biological beneficial of NK-01 were investigated. Our proteomic study will provide further theoretical basis for application of NK in prevention or adjuvant treatment in biomedicine areas.

Characterization of an Atypical Metalloproteinase Inhibitors Like Protein (Sbp8-1) From Scallop Byssus.

Adhesion is a vital physiological process for many marine molluscs, including the mussel and scallop, and therefore it is important to characterize the proteins involved in these adhesives. Although several mussel byssal proteins were identified and characterized, the study for scallop byssal proteins remains scarce. Our previous study identified two foot-specific proteins (Sbp7, Sbp8-1), which were annotated as the tissue inhibitors of metalloproteinases (TIMPs). Evolutionary analysis suggests that the TIMP genes of Chlamys farreri had gone through multiple gene duplications during evolution, and their potential functional roles in foot may have an ancient evolutionary origin. Focusing on the Sbp8-1, the sequence alignment and biochemical analyses suggest that Sbp8-1 is an atypical TIMP. One significant feature is the presence of two extra free Cys residues at its C-terminus, which causes the Sbp8-1 polymerization. Considering the fact that the no inhibitory activity was observed and it is mainly distributed in byssal thread and plaque, we proposed that this atypical Sbp8-1 may play as the cross-linker in scallop byssus. This study facilitates not only the understanding of scallop byssus assembly, also provides the inspiration of water-resistant materials design.