2-(3-(4-methoxyphenoxy)propyl)propane-1,3-diethanethioate is synthesized from 4-methoxyphenol and 1,3-dibromopropane after five-step reaction.The overall yield is 21.2%.The key intermediates and the target compound ar...2-(3-(4-methoxyphenoxy)propyl)propane-1,3-diethanethioate is synthesized from 4-methoxyphenol and 1,3-dibromopropane after five-step reaction.The overall yield is 21.2%.The key intermediates and the target compound are analysized by 1HNMR,13CNMR,IR and MS.展开更多
The surface hydrophobization and flotation of a xanthate−hydroxamate collector toward copper oxide mineral were compared with the combined collectors of xanthate and hydroxamate through water contact angle(WCA)and mic...The surface hydrophobization and flotation of a xanthate−hydroxamate collector toward copper oxide mineral were compared with the combined collectors of xanthate and hydroxamate through water contact angle(WCA)and micro-flotation experiments.The results showed that S-[(2-hydroxyamino)-2-oxoethyl]-O-octyl-dithiocarbonate ester(HAOODE)exhibited stronger hydrophobization and better flotation performance to malachite(Cu2(OH)2CO3)than octyl-hydroxamic acid(OHA)and its combination with S-allyl-O-ethyl xanthate ester(AEXE).To understand the hydrophobic intensification mechanism of HAOODE to malachite,zeta potential,atomic force microscopy(AFM)and XPS measurements were carried out.The results recommended that malachite chemisorbed HAOODE to form Cu—HAOODE complexes in which the hydroxamate—(O,O)—Cu and—O—C(—S—Cu)—S—configurations co-existed.The co-adsorption of HAOODE’s hetero-difunctional groups was more stable than the single-functionalgroup adsorption of OHA and AEXE,which produced the“loop”structure and intensified the self-assembly alignment of HAOODE on malachite surfaces.In addition,the“h”shape steric orientation of the double hydrophobic groups in HAOODE facilitated stronger hydrophobization toward malachite than the“line”or“V”hydrophobic carbon chains of OHA or AEXE.Thus,HAOODE achieved the preferable flotation recovery of malachite particles in comparison with OHA and AEXE.展开更多
The decay dynamics of N, N-dimethylthioacetamide after excitation to the S3（ππ＊） state was studied by using the resonance Raman spectroscopy and complete active space self- consistent field method calculations. T...The decay dynamics of N, N-dimethylthioacetamide after excitation to the S3（ππ＊） state was studied by using the resonance Raman spectroscopy and complete active space self- consistent field method calculations. The UV-absorption and vibrational spectra were as- signed. The A-band resonance Raman spectra were obtained in acetonitrile, methanol and water with the laser excitation wavelengths in resonance with the first intense absorption band to probe the Franck-Condon region structural dynamics. The CASSCF calculations were carried out to determine the excitation energies and optimized structures of the lower- lying singlet states and conical intersection point. The A-band structural dynamics and the corresponding decay mechanism were obtained by the analysis of the resonance Raman in- tensity pattern and the CASSCF calculated structural parameters. The major decay channel of S3,FC （ππ＊）→S3（ππ＊）/S1 （nπ＊）→S1（nπ＊） is proposed.展开更多
A new mixed-metal sulfido incomplete cubane cluster [(MoCuS3) (O) (μ-dtp) (PPh3)3] Cdtp = S2P (OC2H5)2] has been prepared by reaction of (NH4)2MoOS3 with Cu(dtp) (PPh3)2 in dimethylformamide solution. It crystallizes...A new mixed-metal sulfido incomplete cubane cluster [(MoCuS3) (O) (μ-dtp) (PPh3)3] Cdtp = S2P (OC2H5)2] has been prepared by reaction of (NH4)2MoOS3 with Cu(dtp) (PPh3)2 in dimethylformamide solution. It crystallizes in the triclinic space group P1, a = 13.810(5), b = 19. 753(5), c=11. 719(4) A. α=99. 42(2), β=107. 24(3),γ=88. 05(3)°, V = 3012(2)A3, Dc = l. 51g/cm3and Z = 2. Final R=0. 046, Rw = 0. 056 for 7700 unique intensity data(I≥3σ(I)). The central unit [MoCu3S3]3+ can be described as a distorted incomplete cube with one missing corner. The Mo atom is tetrahedrally coordinated by three μ3-S atoms and one terminal O atom. Two Cu atoms are tetrahedrally coordinated whereas the third Cu atom has a highly distorted trigonal environment. The mean Mo - Cu bond length is 2. 752A. The Cu...Cu distances are in the range of 3. 200(1) -3. 740(1) A which are too long to form bonds.展开更多
A mononuclear complex, cis-[meso-1, 3-bis(propylsulfinyl)propane]- dichloroplatinum(Ⅱ) (Pt(C9H20O2S2)Cl2) 1, has been prepared and structurally characterizated by single-crystal X-ray diffraction. The crystal belongs...A mononuclear complex, cis-[meso-1, 3-bis(propylsulfinyl)propane]- dichloroplatinum(Ⅱ) (Pt(C9H20O2S2)Cl2) 1, has been prepared and structurally characterizated by single-crystal X-ray diffraction. The crystal belongs to orthorhombic system, space group Pna21 with a = 22.800(3), b = 11.7662(13), c = 5.8115(6) ? V = 1559.0(3) ?, Mr = 490.36, Dc = 2.089 g/cm3, Z = 4, F(000) = 936, m (MoKa) = 9.596 mm-1 and l = 0.71073 ? The structure was refined to R = 0.0204 and wR = 0.0473 for 2703 reflections with I > 2(I). It is revealed that the central Pt(Ⅱ) ion in the title complex is bonded to two Cl atoms in a cis-configuration and two S atoms of the ligand to form the coordination geometry deviating slightly from the square planar.展开更多
A neutral metalloprotease was purified from the cultured mycelia of Laccocephalum mylittae,an effective medicinal fungus widely used in anthelmintic therapy.The protease was purified to homogeneity with 31.85-fold pur...A neutral metalloprotease was purified from the cultured mycelia of Laccocephalum mylittae,an effective medicinal fungus widely used in anthelmintic therapy.The protease was purified to homogeneity with 31.85-fold purification and a final yield of 21.76%.The subunit molecular weight of the protease is about 40000 estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE).The optimum reaction pH and temperature are 7.5 and 50oC,respectively.The protease activity is largely enhanced by Ca2 +,but highly inhibited by tetrasodium ethylenediaminetetraacetate(EDTA),a metal-chelator,suggesting that the enzyme is a metalloprotease.The Michaelis-Menten constan Km and Vmax value for casein substrate are 6.09 mg·ml -1and 21.32μg·min -1·ml -1, respectively.In vitro anthelmintic tests of the protease exhibit distinct lethal effects on the third stage larvae(L3)of Ascaris suum.Scanning electron microscopy and SDS-PAGE analysis indicates that the proteolysis of larvae proteins caused by this protease may relate to the anthelmintic activity of L.mylittae.展开更多
Four arsenic-resistance genes(arsB,arsC,arsH,arsR) have been discovered in Acidithiobacillus ferrooxidans.Their gene sequences have been identified and three different arsenic-resistance mechanisms have been elucidate...Four arsenic-resistance genes(arsB,arsC,arsH,arsR) have been discovered in Acidithiobacillus ferrooxidans.Their gene sequences have been identified and three different arsenic-resistance mechanisms have been elucidated.However,the function of the arsH gene in At.ferrooxidans remains unclear.In order to evaluate the function of the arsH gene,we cloned it and expressed it in Escherichia coli.The protein was purified and its relative molecular mass was determined by SDS-PAGE(Sodium dodecyl sulfate-polyacrylamide gel electrophoresis).The results indicated that the relative molecular mass of the purified ArsH was approximately 29 kDa.The purified protein ArsH from E.coli BL21 was a flavoprotein that oxidized in vitro NADPH with an optimal pH of 6.4.展开更多
Escherichia coli type 1 was used as a model system to determine whether static magnetic fields are a general stress factor. The bacterial broth culture were exposed to different magnetic force （400, 800, 1200 and 160...Escherichia coli type 1 was used as a model system to determine whether static magnetic fields are a general stress factor. The bacterial broth culture were exposed to different magnetic force （400, 800, 1200 and 1600 Gauss） with incubation at 37 ℃ for different times （24, 48 and 72 hrs） under aerobic conditions. The response of the cells to the magnetic fields was estimated from the change in total protein synthesis by using spectrophotometer at 550 nm and by using of SDS-PAGE （Sodium dodecyl sulfate- polyacrylamide gel electrophoresis）. Results concluded that was approximately no reproducible changes qualitatively in extracellular proteins were observed in the SDS-PAGE electrophoresis and did not act as a general stress factor. While, increases in the level of extra-cellular synthesis were observed using different magnetic field exposed samples when compared with the control.展开更多
Our previous studies have shown that zein has good biocompatibility and good mechanical properties. The first product from a porous scaffold of zein, a resorbable bone substitute, has passed the biological evaluation ...Our previous studies have shown that zein has good biocompatibility and good mechanical properties. The first product from a porous scaffold of zein, a resorbable bone substitute, has passed the biological evaluation of medical devices （ISO 10993） by the China Food and Drug Administration. However, Class III medical devices need quality monitoring before being placed on the market, and such monitoring includes quality control of raw materials, choice of sterilization method, and evaluation of biocompatibility. In this paper, we investigated four sources of zein through amino acid analysis （AAA） and sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE） in order to monitor the composition and purity, and control the quality of raw materials. We studied the effect of three kinds of sterilization method on a porous zein scaffold by SDS-PAGE. We also compared the changes in SDS-PAGE patterns when irradiated with different doses of gamma radiation. We found that polymerization or breakage did not occur on peptide chains of zein during gamma-ray （y-ray） sterilization in the range of 20-30 kGy, which suggested that γ-ray sterilization is suitable for porous zein scaffolds, Regarding cell compatibility, we found a difference between using a 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyl tetrazolium bromide （MTT） assay and a cell-counting kit-8 （CCK-8） assay to assess cell proliferation on zein film, and concluded that the CCK-8 assay is more suitable, due to its low background optical density.展开更多
The difference in accumulation of high molecular weight glutenin subunits （HMW-GS） in superior and inferior grains results in the non-uniformity of grain quality in winter wheat （Triticum aestivum L.）. The HMW-GS ...The difference in accumulation of high molecular weight glutenin subunits （HMW-GS） in superior and inferior grains results in the non-uniformity of grain quality in winter wheat （Triticum aestivum L.）. The HMW-GS accumulation and glutenin macropolymer （GMP） content were studied in superior and inferior grains during the grain filling period, using the sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）. Compared to inferior grains, HMW-GS was formed earlier and total accumulation amount was higher in superior grains. The total HMW-GS content was higher in superior grain than that in inferior grain except at maturity. For individual HMW-GS types, the accumulation and content of subunit 7 were the highest, followed by subunit 12, while that of subunit 8 were the lowest, followed by subunit 2 in superior grain. In contrary, the accumulation and content of subunit 7 at maturity were significantly higher than subunit 8, but they were similar between subunit 2 and subunit 12 in inferior grain. Moreover, the accumulation of subunit 7 and 12 in superior grain were significantly higher than that in inferior grain. However, compared to the inferior grain, the GMP accumulation was higher, while content was lower in superior grain at maturity.展开更多
To characterize the antigenicity of nucleocapsid proteins(NP) derived from canine coronavirus(CCo V) and canine respiratory coronavirus(CRCo V) in China, the N genes of CCo V(CCo V-BJ70) and CRCo V(CRCo V-BJ202) were ...To characterize the antigenicity of nucleocapsid proteins(NP) derived from canine coronavirus(CCo V) and canine respiratory coronavirus(CRCo V) in China, the N genes of CCo V(CCo V-BJ70) and CRCo V(CRCo V-BJ202) were cloned from swabs obtained from diseased pet dogs in Beijing and then sequenced. The recombinant NPs(r NPs) were expressed in Escherichia coli and purified by nickel-affinity column and size exclusion chromatography. Sequencing data indicated that the N genes of CCo V-BJ70 and CRCo V-BJ202 belonging to two distinctly different groups were relatively conserved within each subgroup. Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) results showed that r NPs of CCo V and CRCo V were expressed efficiently and isolated with a final purity of over 95%. Western blot analysis revealed the r NP from CRCo V could cross-react with mice antisera against human coronavirus(HCo V-229 E, NL63, OC43, HKU1), while r NP of CCo V had cross-reactivity with only anti-sera against viruses belonging to the same group(HCo V-229 E and NL63). In summary, CCo V and CRCo V r NPs were successfully expressed in E. coli and showed antigenic cross-reactivity with antisera raised against human coronaviruses. These findings indicate that further serologic studies on coronavirus infections at the animal-human interface are needed.展开更多
文摘2-(3-(4-methoxyphenoxy)propyl)propane-1,3-diethanethioate is synthesized from 4-methoxyphenol and 1,3-dibromopropane after five-step reaction.The overall yield is 21.2%.The key intermediates and the target compound are analysized by 1HNMR,13CNMR,IR and MS.
基金Project(51474253)supported by the National Natural Science Foundation of China。
文摘The surface hydrophobization and flotation of a xanthate−hydroxamate collector toward copper oxide mineral were compared with the combined collectors of xanthate and hydroxamate through water contact angle(WCA)and micro-flotation experiments.The results showed that S-[(2-hydroxyamino)-2-oxoethyl]-O-octyl-dithiocarbonate ester(HAOODE)exhibited stronger hydrophobization and better flotation performance to malachite(Cu2(OH)2CO3)than octyl-hydroxamic acid(OHA)and its combination with S-allyl-O-ethyl xanthate ester(AEXE).To understand the hydrophobic intensification mechanism of HAOODE to malachite,zeta potential,atomic force microscopy(AFM)and XPS measurements were carried out.The results recommended that malachite chemisorbed HAOODE to form Cu—HAOODE complexes in which the hydroxamate—(O,O)—Cu and—O—C(—S—Cu)—S—configurations co-existed.The co-adsorption of HAOODE’s hetero-difunctional groups was more stable than the single-functionalgroup adsorption of OHA and AEXE,which produced the“loop”structure and intensified the self-assembly alignment of HAOODE on malachite surfaces.In addition,the“h”shape steric orientation of the double hydrophobic groups in HAOODE facilitated stronger hydrophobization toward malachite than the“line”or“V”hydrophobic carbon chains of OHA or AEXE.Thus,HAOODE achieved the preferable flotation recovery of malachite particles in comparison with OHA and AEXE.
基金This work was supported by the National Natu- ral Science Foundation of China （No.21033002 and No.21202032） and the National Basic Research Pro- gram of China （No.2013CB834604）.
文摘The decay dynamics of N, N-dimethylthioacetamide after excitation to the S3（ππ＊） state was studied by using the resonance Raman spectroscopy and complete active space self- consistent field method calculations. The UV-absorption and vibrational spectra were as- signed. The A-band resonance Raman spectra were obtained in acetonitrile, methanol and water with the laser excitation wavelengths in resonance with the first intense absorption band to probe the Franck-Condon region structural dynamics. The CASSCF calculations were carried out to determine the excitation energies and optimized structures of the lower- lying singlet states and conical intersection point. The A-band structural dynamics and the corresponding decay mechanism were obtained by the analysis of the resonance Raman in- tensity pattern and the CASSCF calculated structural parameters. The major decay channel of S3,FC （ππ＊）→S3（ππ＊）/S1 （nπ＊）→S1（nπ＊） is proposed.
文摘A new mixed-metal sulfido incomplete cubane cluster [(MoCuS3) (O) (μ-dtp) (PPh3)3] Cdtp = S2P (OC2H5)2] has been prepared by reaction of (NH4)2MoOS3 with Cu(dtp) (PPh3)2 in dimethylformamide solution. It crystallizes in the triclinic space group P1, a = 13.810(5), b = 19. 753(5), c=11. 719(4) A. α=99. 42(2), β=107. 24(3),γ=88. 05(3)°, V = 3012(2)A3, Dc = l. 51g/cm3and Z = 2. Final R=0. 046, Rw = 0. 056 for 7700 unique intensity data(I≥3σ(I)). The central unit [MoCu3S3]3+ can be described as a distorted incomplete cube with one missing corner. The Mo atom is tetrahedrally coordinated by three μ3-S atoms and one terminal O atom. Two Cu atoms are tetrahedrally coordinated whereas the third Cu atom has a highly distorted trigonal environment. The mean Mo - Cu bond length is 2. 752A. The Cu...Cu distances are in the range of 3. 200(1) -3. 740(1) A which are too long to form bonds.
基金This work was financially supported by the NSFC (No. 29971019)
文摘A mononuclear complex, cis-[meso-1, 3-bis(propylsulfinyl)propane]- dichloroplatinum(Ⅱ) (Pt(C9H20O2S2)Cl2) 1, has been prepared and structurally characterizated by single-crystal X-ray diffraction. The crystal belongs to orthorhombic system, space group Pna21 with a = 22.800(3), b = 11.7662(13), c = 5.8115(6) ? V = 1559.0(3) ?, Mr = 490.36, Dc = 2.089 g/cm3, Z = 4, F(000) = 936, m (MoKa) = 9.596 mm-1 and l = 0.71073 ? The structure was refined to R = 0.0204 and wR = 0.0473 for 2703 reflections with I > 2(I). It is revealed that the central Pt(Ⅱ) ion in the title complex is bonded to two Cl atoms in a cis-configuration and two S atoms of the ligand to form the coordination geometry deviating slightly from the square planar.
基金Supported by the National High Technology Research and Development Program of China（2007AA021506） the Natural Science Foundation of Zhejiang Province（R207609）
文摘A neutral metalloprotease was purified from the cultured mycelia of Laccocephalum mylittae,an effective medicinal fungus widely used in anthelmintic therapy.The protease was purified to homogeneity with 31.85-fold purification and a final yield of 21.76%.The subunit molecular weight of the protease is about 40000 estimated by sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE).The optimum reaction pH and temperature are 7.5 and 50oC,respectively.The protease activity is largely enhanced by Ca2 +,but highly inhibited by tetrasodium ethylenediaminetetraacetate(EDTA),a metal-chelator,suggesting that the enzyme is a metalloprotease.The Michaelis-Menten constan Km and Vmax value for casein substrate are 6.09 mg·ml -1and 21.32μg·min -1·ml -1, respectively.In vitro anthelmintic tests of the protease exhibit distinct lethal effects on the third stage larvae(L3)of Ascaris suum.Scanning electron microscopy and SDS-PAGE analysis indicates that the proteolysis of larvae proteins caused by this protease may relate to the anthelmintic activity of L.mylittae.
基金Project(50621063) supported by the National Natural Science Foundation of ChinaProject(2004CB619201) supported by the National Basic Research Program of China
文摘Four arsenic-resistance genes(arsB,arsC,arsH,arsR) have been discovered in Acidithiobacillus ferrooxidans.Their gene sequences have been identified and three different arsenic-resistance mechanisms have been elucidated.However,the function of the arsH gene in At.ferrooxidans remains unclear.In order to evaluate the function of the arsH gene,we cloned it and expressed it in Escherichia coli.The protein was purified and its relative molecular mass was determined by SDS-PAGE(Sodium dodecyl sulfate-polyacrylamide gel electrophoresis).The results indicated that the relative molecular mass of the purified ArsH was approximately 29 kDa.The purified protein ArsH from E.coli BL21 was a flavoprotein that oxidized in vitro NADPH with an optimal pH of 6.4.
文摘Escherichia coli type 1 was used as a model system to determine whether static magnetic fields are a general stress factor. The bacterial broth culture were exposed to different magnetic force （400, 800, 1200 and 1600 Gauss） with incubation at 37 ℃ for different times （24, 48 and 72 hrs） under aerobic conditions. The response of the cells to the magnetic fields was estimated from the change in total protein synthesis by using spectrophotometer at 550 nm and by using of SDS-PAGE （Sodium dodecyl sulfate- polyacrylamide gel electrophoresis）. Results concluded that was approximately no reproducible changes qualitatively in extracellular proteins were observed in the SDS-PAGE electrophoresis and did not act as a general stress factor. While, increases in the level of extra-cellular synthesis were observed using different magnetic field exposed samples when compared with the control.
文摘Our previous studies have shown that zein has good biocompatibility and good mechanical properties. The first product from a porous scaffold of zein, a resorbable bone substitute, has passed the biological evaluation of medical devices （ISO 10993） by the China Food and Drug Administration. However, Class III medical devices need quality monitoring before being placed on the market, and such monitoring includes quality control of raw materials, choice of sterilization method, and evaluation of biocompatibility. In this paper, we investigated four sources of zein through amino acid analysis （AAA） and sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE） in order to monitor the composition and purity, and control the quality of raw materials. We studied the effect of three kinds of sterilization method on a porous zein scaffold by SDS-PAGE. We also compared the changes in SDS-PAGE patterns when irradiated with different doses of gamma radiation. We found that polymerization or breakage did not occur on peptide chains of zein during gamma-ray （y-ray） sterilization in the range of 20-30 kGy, which suggested that γ-ray sterilization is suitable for porous zein scaffolds, Regarding cell compatibility, we found a difference between using a 3-（4,5-dimethylthiazol-2-yl）-2,5-diphenyl tetrazolium bromide （MTT） assay and a cell-counting kit-8 （CCK-8） assay to assess cell proliferation on zein film, and concluded that the CCK-8 assay is more suitable, due to its low background optical density.
基金This study is supported by the projects of Priority Academic Program Developmem （PAPD）, the National Natural Science Foundation of China （31171484, 31471445）, the National Natural Science Foundation for Distinguished Young Scientists （31325020）, Jiangsu Agriculture Science and Technology Innovation Fund （CX （14） 2002）, the Specialized Research Fund for the Doctoral Program of Higher Education （20090097110009）, the National Non-profit Program by Ministry of Agriculture （200903003）, and the China Agriculture Research System （CARS-03）.
文摘The difference in accumulation of high molecular weight glutenin subunits （HMW-GS） in superior and inferior grains results in the non-uniformity of grain quality in winter wheat （Triticum aestivum L.）. The HMW-GS accumulation and glutenin macropolymer （GMP） content were studied in superior and inferior grains during the grain filling period, using the sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）. Compared to inferior grains, HMW-GS was formed earlier and total accumulation amount was higher in superior grains. The total HMW-GS content was higher in superior grain than that in inferior grain except at maturity. For individual HMW-GS types, the accumulation and content of subunit 7 were the highest, followed by subunit 12, while that of subunit 8 were the lowest, followed by subunit 2 in superior grain. In contrary, the accumulation and content of subunit 7 at maturity were significantly higher than subunit 8, but they were similar between subunit 2 and subunit 12 in inferior grain. Moreover, the accumulation of subunit 7 and 12 in superior grain were significantly higher than that in inferior grain. However, compared to the inferior grain, the GMP accumulation was higher, while content was lower in superior grain at maturity.
基金supported by the Mega project for Infectious Disease Research of China (2014ZX10004001-002, 2013ZX10004601)National Basic Research Program of China (2011CB504704)
文摘To characterize the antigenicity of nucleocapsid proteins(NP) derived from canine coronavirus(CCo V) and canine respiratory coronavirus(CRCo V) in China, the N genes of CCo V(CCo V-BJ70) and CRCo V(CRCo V-BJ202) were cloned from swabs obtained from diseased pet dogs in Beijing and then sequenced. The recombinant NPs(r NPs) were expressed in Escherichia coli and purified by nickel-affinity column and size exclusion chromatography. Sequencing data indicated that the N genes of CCo V-BJ70 and CRCo V-BJ202 belonging to two distinctly different groups were relatively conserved within each subgroup. Sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE) results showed that r NPs of CCo V and CRCo V were expressed efficiently and isolated with a final purity of over 95%. Western blot analysis revealed the r NP from CRCo V could cross-react with mice antisera against human coronavirus(HCo V-229 E, NL63, OC43, HKU1), while r NP of CCo V had cross-reactivity with only anti-sera against viruses belonging to the same group(HCo V-229 E and NL63). In summary, CCo V and CRCo V r NPs were successfully expressed in E. coli and showed antigenic cross-reactivity with antisera raised against human coronaviruses. These findings indicate that further serologic studies on coronavirus infections at the animal-human interface are needed.
