Alkylated poly(amino acids). I. Conformational properties of poly(Nε-trimethyl-L-lysine) and poly(Nδ-trimethyl-L-ornithine)

Poly(N^ε-trimethyl-L -lysine), [Lys(Me₃)]_n, and poly(N^δ-trimethyl-L -ornithine), [Orn(Me₃)]_n, in sodium dodecylsulfate do not assume the β-structure or α-helix, respectively, of their parent polymers. In 0.5M Ca(ClO₄)₂ both [Lys(Me₃)]_n and [Orn(Me₃)]_n are aggregated and display CD spectra indicative of a regular, perhaps helical, structure. For [Lys]_n and [Lys(Me₃)]_n, the T₁ of the α-hydrogens are 0.379 and 0.230 sec, respectively, indicating greater rigidity for [Lys(Me₃)]_n. The CD spectrum of [Lys(Me₃)]_n at pH 8 is more heat resistant than that of [Lys]_n. It is suggested that apolar interactions are more important in the methylated polymers than in the parent polymers.     

Formation and stability of helical poly(N epsilon,N epsilon,N epsilon-trimethyl-L-lysine) in sodium perchlorate solution

Poly(trimethyl-L-lysine), [Lys(Me₃)]_n, is converted from random coil to α-helix at about 1/30 of the NaClO₄ concentration required by poly(L-lysine), (Lys)_n. NaClO₄ generates turbidity in [Lys(Me)₃]_n at concentrations above that required for helix formation, and decreases turbidity above lM NaClO₄. The turbidity runs parallel to enhanced, and then decreased, fluorescence of a dansyl label. Helix formation per se does not induce enhanced fluorescence. Increasing NaClO₄ concentration increases T_m linearly with log[NaClO₄] for both (Lys)_n and [Lys(Me₃)]_n until the denaturing effect of high NaClO₄ sets in. Increasing NaClO₄ also increases the breadth of the transition. Heating helical [Lys(Me₃)]_n or (Lys)_n does not produce a CD spectrum resembling that of “random-coil” (Lys)_n, except for [Lys(Me₃)]_n at relatively low NaClO₄ concentration.     

CD studies of double-stranded polydeoxynucleotides composed of repeating units of contiguous homopurine residues

Double-stranded synthetic polydeoxynucleotides of the general form poly[d(G_nC_n)] · poly[d(G_nC_n)], poly[d(G_nC)] · poly[d(GC_n)], and poly[d(A_nT_n)] · poly[d(A_nT_n)] have been synthesized. When n = 4 or larger, the CD spectra of polymers of the form poly[d(G_nC_n)] · poly[d(G_nC_n)] or poly[d(G_nC)] · poly[d(GC_n)] closely resemble the spectrum of poly[dG] · poly[dC], suggesting that a string of four continguous guanosine residues is sufficient to induce a conformation resembling that of the polypurine · polypyrimidine. With polymers of the form poly[d(A_nT_n)] · poly[d(A_nT_n)], however, the CD spectrum only gradually approaches that of poly[dA] · poly[dT].     

15N-NMR spectroscopy. IV. Comparison of poly(L-lysine) and isopoly(L-lysine)

The natural abundance ¹⁵N-nmr spectroscopy has been used to characterize the isomeric polymers (L -Lys)_n and iso (L -Lys)_n in aqueous solution. Although the peptide nitrogens of the two polymers have nearly equivalent shifts at pH < 10, the amino nitrogens differ by 5–6 ppm at pH < 7 and provide an easy means of identification. Furthermore, the polymers are distinguishable by the pK_a of the amino group and the basicity of the peptide nitrogen. At pH 10.3 and 25°C, (Lys)_n exhibits line broadening and an upfield chemical shift of the peptide nitrogen, indicative of the coil → helix transition. The formation of 100% helix may produce a shift as large as 5 ppm, which probably makes ¹⁵N-nmr spectroscopy more suitable for studies of this transition.     

Phenoxyl-copper(II) complexes: models for the active site of galactose oxidase

 The reaction of the macrocycles 1,4,7-tris (3,5-di-tert-butyl-2-hydroxy-benzyl)-1,4,7-triazacyclononane, L¹H₃, or 1,4,7-tris(3-tert-butyl-5-methoxy-2-hydroxy-benzyl)-1,4,7-triazacyclononane, L²H₃, with Cu(ClO₄)₂·6H₂O in methanol (in the presence of Et₃N) affords the green complexes [Cu^II(L¹H)] (1), [Cu^II(L²H)]·CH₃OH (2) and (in the presence of HClO₄) [Cu^II(L¹H₂)](ClO₄) (3) and [Cu^II(L²H₂)] (ClO₄) (4). The Cu^II ions in these complexes are five-coordinate (square-base pyramidal), and each contains a dangling, uncoordinated pendent arm (phenol). Complexes 1 and 2 contain two equatorially coordinated phenolato ligands, whereas in 3 and 4 one of these is protonated, affording a coordinated phenol. Electrochemically, these complexes can be oxidized by one electron, generating the phenoxyl-copper(II) species [Cu^II(L¹H)]^+ ·, [Cu(L²H)]^+ ·, [Cu^II(L¹H₂)]^2+ ·, and [Cu^II(L²H₂)]^2+ ·, all of which are EPR-silent. These species are excellent models for the active form of the enzyme galactose oxidase (GO). Their spectroscopic features (UV-VIS, resonance Raman) are very similar to those reported for GO and unambiguously show that the complexes are phenoxyl-copper(II) rather than phenolato-copper(III) species. Received: 10 February 1997 / Accepted: 7 April 1997     

Proton transfer and polarizability of hydrogen bonds formed between cysteine and lysine residues

(L -Cys)_n + N-base systems and (L -Cys)_n + (L -Lys)_n systems were studied by ir spectroscopy. It is shown that in the water-free systems, SH ?N ? S^? ?H⁺N hydrogen bonds are formed. With the (L -Cys)_n + N-base systems, both proton-limiting structures in the SH ?N ? S^? ?H⁺N bonds have equal weight when the pK_a of the protonated N-base is 2 pK_a units larger than that of (L -Cys)_n. The same is true with the water-free (L -Cys)_n + (L -Lys)_n system. Thus, with regard to the type of proton potentials present, these hydrogen bonds are proton-transfer hydrogen bonds showing very large proton polarizabilities. This is confirmed by the occurrence of continua in the ir spectra. Small amounts of water open these hydrogen bonds and increase the transfer of the proton to (L -Lys)_n. In the (L -Lys)_n + N-base systems, with increasing proton transfer the backbone of (L -Cys)_n changes from antiparallel β-structure to coil. In (L -Cys)_n + (L -Lys)_n, the conformation is determined by the (L -Lys)_n conformation and changes depending on the chain length of (L -Lys)_n. Finally, the reactivity increase in the active center of fatty acid synthetase, which should be caused by the shift of a proton, is discussed on the basis of the great proton polarizability of the cysteine–lysine hydrogen bonds.     

Chlorine dioxide inactivation of bacterial threat agents

Aims: To evaluate the efficacy of chlorine dioxide (ClO₂) against seven species of bacterial threat (BT) agents in water. Methods and Results: Two strains of Bacillus anthracis spores, Yersinia pestis, Francisella tularensis, Burkholderia pseudomallei, Burkholderia mallei and Brucella species were each inoculated into a ClO₂ solution with an initial concentration of 2·0 (spores only) and 0·25 mg l^?1 (all other bacteria) at pH 7 or 8, 5 or 25°C. At 0·25 mg l^?1 in potable water, six species were inactivated by at least three orders of magnitude within 10 min. Bacillus anthracis spores required up to 7 h at 5°C for the same inactivation with 2·0 mg l^?1 ClO₂. Conclusions: Typical ClO₂ doses used in water treatment facilities would be effective against all bacteria tested except B. anthracis spores that would require up to 7 h with the largest allowable dose of 2 mg l^?1 ClO₂. Other water treatment processes may be required in addition to ClO₂ disinfection for effective spore removal or inactivation. Significance and Impact of Study: The data obtained from this study provide valuable information for water treatment facilities and public health officials in the event that a potable water supply is contaminated with these BT agents.     

Reactivity of an extremenly sterically crowded monofunctional Pt complex, [Pt(1-MeC-N3)3(H2O)]2+ (1-MeC=1-methylcytosine), toward model nucleobases and selectivity toward guanine in single- and double-stranded deoxyoligonucleotides

 Reactions of [Pt(1-MeC-N3)₃Cl]NO₃ (1-MeC-N3=1-methylcytosine, bound to Pt via N3) and the respective aqua species [Pt(1-MeC-N3)₃(H₂O)]²⁺ with the model nucleobases 9-ethylguanine (9-EtGH), 9-methyladenine (9-MeA), single-stranded 5′d(T₃GT₃), and double-stranded [5′d(GAGA₂GCT₂CTC)]₂ have been studied in solution by means of ¹H NMR spectroscopy, HPLC, and electrospray ionization mass spectrometry. Reactions are generally slow, in particular with the chloro species, and guanine is the only reactive base in the oligonucleotides. However, unlike (dien)Pt^II, which binds randomly to the guanines in the ds dodecamer, (1-MeC-N3)₃Pt^II binds selectively to the terminal guanine only, probably because base fraying takes place at the duplex ends. The X-ray crystal structures of [Pt(1-MeC-N3)₃(9-EtG-N7)]ClO₄·8H₂O (1b) and of [Pt(1-MeC-N3)₃(9-MeA-N7)](ClO₄)₂·0.5H₂O as well as NMR spectroscopic studies of [Pt(1-MeC-N3)₃(9-EtGH-N7)] (NO₃)₂·H₂O (1a) are reported. The tetrakis(nucleobase) complexes adopt a head-tail-head orientation of the three 1-MeC bases and an orientation of the fourth base (purine) that permits a maximum of intracomplex H bonds between exocyclic groups. As far as the guanine adduct (1a, 1b) is concerned, relative orientations of the four bases are identical in the model and in the oligonucleotide adduct. Received: 19 June 1998 / Accepted: 1 October 1998     

The effect of different kinds of electrolyte and non‐electrolyte solutions on the survival rate and morphology of zebrafish Danio rerio embryos

The effect of electrolyte and non‐electrolyte solutions on the survival and on the morphology of zebrafish Danio rerio embryos was investigated. Embryos in different ontogenetic stages were incubated in electrolyte (NaCl, KCl, MgCl₂ and CaCl₂) and non‐electrolyte solutions [sucrose and polyvinylalcohol (PVA)] of different concentrations for 5 – 15 min. The embryos were hatched to the long‐pec stage and the effective concentrations which caused a 50% decrease in embryo development (EC₅₀) were determined. The morphometric changes, which were caused by the test solutions, were measured. Ion channel blockers were used to see if active ion transport played a role for embryo survival. Finally, dechorionated embryos were exposed to the test solutions to get indications about the importance of chorion and perivitelline space. For 12 hours post fertilization (hpf) embryos and a 15 min exposure period, EC₅₀ was highest for MgCl₂ (1·60 mol l^?1), followed by sucrose (0·73 mol l^?1), NaCl (0·49 mol l^?1), KCl (0·44 mol l^?1), CaCl₂ (0·43 mol l^?1) and PVA [0·0005 mol l^?1 (2·2%)]. EC₅₀ were lower for early embryonic stages than for advanced stages for all solutions with exception of MgCl₂ and sucrose. At the EC₅₀, MgCl₂ and CaCl₂ solutions did not induce morphometric changes. NaCl and sucrose solutions induced reversible morphometric changes, which were compensated within 10 min. Only the EC₅₀ of KCl and PVA solutions induced permanent morphometric changes, which could not be compensated. Incubation of embryos in electrolyte and non‐electrolyte solutions together with ouabain (blocker of Na⁺– K⁺ ATPase), HgCl₃ (dose‐dependent inhibition of aquaporine channels), verapamil (inhibition of calcium and magnesium uptake) and amiloride (inhibition of sodium uptake) significantly decreased the per cent of embryos developing to the long‐pec stage in comparison to the same solutions without blockers. Ouabain and HgCl₃ also induced morphometric changes. For dechorionated embryos the survival rates in water and in the different test solutions were similar to untreated embryos.     

Synthesis and biological evaluation of tricarbonyl Re(I) and Tc(I) complexes anchored by poly(azolyl)borates: application on the design of radiopharmaceuticals for the targeting of 5-HT<Subscript>1A</Subscript> receptors

The building blocks fac-[^99mTc{κ³-HB(tim^Me)₃}(CO)₃] and fac-[^99mTc{κ³-R(μ-H)B(tim^Me)₂}(CO)₃] [R is H (4a), Ph (5a); tim^Me is 2-mercapto-1-methylimidazolyl] were obtained almost quantitatively by reacting fac-[^99mTc(CO)₃(H₂O)₃]⁺ with the corresponding scorpionate. These compounds cross the intact blood–brain barrier in mice, with significant retention in the case of 4a and 5a. Using 4a as the lead structure, we have synthesized the functionalized complexes fac-[M{κ³-H(μ-H)B(tim^Bu-pip)₂}(CO)₃] [M is Re (8), ^99mTc (8a); tim^Bu-pip is methyl[4-((2-methoxyphenyl)-1-piperazinyl)butyl](2-mercapto-1-methylimidazol-5-yl)methanamide] and fac-[M{κ ³-H(μ-H)B(tim^Me)(tim^Bu-pip)}(CO)₃] [M is Re (9), ^99mTc (9a)] and evaluated their potential as radioactive probes for the targeting of brain 5-HT_1A serotonergic receptors. The Re complexes exhibit excellent affinity [IC₅₀=0.172 ± 0.003 nM (8); IC₅₀=0.65 ± 0.01 nM (9)] for the 5-HT_1A receptor. The radioactive congeners (^99mTc) have shown an initial brain uptake of 1.38 ± 0.46%ID g⁻¹ (8a) and 0.43 ± 0.12%ID g⁻¹ (9a), but suffer from a relatively fast washout.     

Antibacterial,antifungal and in vitro antileukaemia activity of metal complexes with thiosemicarbazones

1‐phenyl‐3‐methyl‐4‐benzoyl‐5‐pyrazolone 4‐ethyl‐thiosemicarbazone (HL) and its copper(II), vanadium(V) and nickel(II) complexes: [Cu(L)(Cl)]·C₂H₅OH·( 1 ), [Cu(L)₂]·H₂O ( 2 ), [Cu(L)(Br)]·H₂O·CH₃OH ( 3 ), [Cu(L)(NO₃)]·2C₂H₅OH ( 4 ), [VO₂(L)]·2H₂O ( 5 ), [Ni(L)₂]·H₂O ( 6 ), were synthesized and characterized. The ligand has been characterized by elemental analyses, IR, ¹H NMR and ¹³C NMR spectroscopy. The tridentate nature of the ligand is evident from the IR spectra. The copper(II), vanadium(V) and nickel(II) complexes have been characterized by different physico‐chemical techniques such as molar conductivity, magnetic susceptibility measurements and electronic, infrared and electron paramagnetic resonance spectral studies. The structures of the ligand and its copper(II) ( 2 , 4 ), and vanadium(V) ( 5 ) complexes have been determined by single‐crystal X‐ray diffraction. The composition of the coordination polyhedron of the central atom in 2 , 4 and 5 is different. The tetrahedral coordination geometry of Cu was found in complex 2 while in complex 4 , it is square planar, in complex 5 the coordination polyhedron of the central ion is distorted square pyramid. The in vitro antibacterial activity of the complexes against Escherichia coli, Salmonella abony, Staphylococcus aureus, Bacillus cereus and the antifungal activity against Candida albicans strains was higher for the metal complexes than for free ligand. The effect of the free ligand and its metal complexes on the proliferation of HL‐60 cells was tested.     

Adducts of titanium tetrahalides with neutral Lewis bases. Part I. Structure and stability: a vibrational and multinuclear NMR study

Raman, infra-red and multinuclear NMR spectroscopy were used to establish the structure of several TiX₄·2L adducts (X=F, Cl, Br; L=Lewis base) in inert solvents. In contrast to the analogous SnX₄·2L adducts where a cis-trans equilibrium prevails, most of the TiX₄·2L adducts studied were found to have only the cis configuration. Trans isomers were observed but their formation was dependent on the donor ability of the ligand. In dichloromethane solution, the adducts with L=Me₂O, Me₂S, (MeOCH₂-)₂, Et₂S, THT, Me₂Se, MeCN, Me₂CO, Cl(MeO)₂PO, Cl₂(MeO)PO, Cl₃PO and Cl₂(Me₂N)PO were found to have the cis configuration only. For the adducts with L=THF, Cl(Me₂N)₂PO and TMPA, a cis-trans equilibrium was observed. The thermodynamic parameters were measured for cis-trans isomerization for TiCl₄·2TMPA in CHCl₃; these parameters are: K_iso²⁷⁷=[trans] / [cis]=0.36, ΔH°_iso=− 1.3 ± 1.3 kJ/mol, ΔS°_iso=−13.1 + 7.5 J/mol K, and ΔV°_iso= − 1.3+0.8 cm³/mol. A complex equilibrium involving cis and trans isomers and the ionic complex [TiCl₃·3HMPA]Cl was found to occur for the TiCl₄ adduct with L=HMPA. ¹H NMR was used to establish the relative stabilities of the cis adducts and the following sequence was obtained: Me₂O ∼ MeCN < Me₂CO < Me₂S < Me₂Se < Cl(MeO)₂PO < TMPA < CI(Me₂N)₂PO.     

Tetra-, penta- and hexacoordinate copper(II) complexes with N3 donor isoindoline-based ligands: Characterization and SOD-like activity

Reaction of 1,3-bis(2′-Ar-imino)isoindolines (HLⁿ, n = 1-7, Ar = benzimidazolyl, N-methylbenzimidazolyl, thiazolyl, pyridyl, 3-methylpyridyl, 4-methylpyridyl, and benzthiazolyl, respectively) with Cu(OCH₃)₂ yields mononuclear hexacoordinate complexes with Cu(Lⁿ)₂ composition. With cupric perchlorate square-pyramidal [Cu^II(HLⁿ)(NCCH₃)(OClO₃)]ClO₄ complexes (n = 1, 3, 4) were isolated as perchlorate salts, whereas with chloride Cu^II(HLⁿ)Cl₂ (n = 1, 4), or square-planar Cu^IICl₂(HLⁿ) (n = 2, 3, 7) complexes are formed. The X-ray crystal structures of Cu(L³)₂, Cu(L⁵)₂, [Cu^II(HL⁴)(NCCH₃)(OClO₃)]ClO₄, Cu^IICl(L²) and Cu^IICl(L⁷) are presented along with electrochemical and spectral (UV-Vis, FT-IR and X-band EPR) characterization for each compound. When combined with base, the isoindoline ligands in the [Cu^II(HLⁿ)(NCCH₃)(OClO₃)]ClO₄ complexes undergo deprotonation in solution that is reversible and induces UV-Vis spectral changes. Equilibrium constants for the dissociation are calculated. X-band EPR measurements in frozen solution show that the geometry of the complexes is similar to the corresponding X-ray crystallographic structures. The superoxide scavenging activity of the compounds determined from the McCord-Fridovich experiment show dependence on structural features and reduction potentials.     

Size‐dependent effects of daily thermal fluctuations on the growth and size heterogeneity of Nile tilapia Oreochromis niloticus

The growth of Nile tilapia Oreochromis niloticus (0·02–20·00 g) was measured when fed to excess during the hours of light, following their exposure to five thermal regimes fluctuating around the thermal optimum for growth (T_opt = 30° C) over the diel cycle of day (light, L) and night (dark, N), i.e. 27° C(L):33° C(N), 28·5° C(L):31·5° C(N), 30° C(L):30° C(N), 31·5° C(L):28·5° C(N) and 33° C(L):27° C(N) (two replicates per treatment, six weeks' rearing, growth measurements at weekly intervals). A model constructed with a stepwise multiple‐regression analysis accounted for 87·4% of the variation of the specific growth rate (G, % M day^?1) from the variations of wet mass (M), the extent of the thermal fluctuation (F_T) and their interactions, i.e. log₁₀G = 1·7686 ? 0·2136 log₁₀M + 0·0806 [log ₁₀M× log ₁₀ (1 + F_T)] ? 0·0394 [log₁₀M× log ₁₀ (1 + F_T)]². Based on this model, the thermal fluctuation that produces the fastest growth ( ,°C) decreases in a curvilinear way, from 5·1° C at 20 mg to c. 0·7° C at 20 g. Thermal regimes that produce the slowest growth also produce the highest size heterogeneity. Functional hypotheses behind the size‐dependent effects of thermal fluctuations are discussed, together with their implications in natural habitats and aquaculture systems with in different contexts of food availability.     

Transient electric birefringence of the bacteriophages T3 and T7

Electric birefringence measurements of suspensions of T3 and T7 bacteriophages in 10^?2 M phosphate buffer, pH 6.9, show that there is a difference in their rotational diffusion coefficient. The values corrected to 25°C and water viscosity are D_25,w = 4630 ± 130 sec^?1 and D_25,w = 5290 ± 260 sec^?1 for T3 and T7, respectively. The value obtained from shell model calculations (according to Filson and Bloomfield) is D_25,w = 4500 ± 600 sec^?1. The apparent permanent dipole moments are 4.5 × 10^?26 C·m and 1.7 × 10^?26 C·m for T3 and T7, respectively. For both phage particles the intrinsic optical anisotropy is +7.2 × 10^?3. It is shown that this anisotropy is mainly due to the DNA molecule inside the head of the phage. Its positive value means that there exists an excess orientation of the DNA helix perpendicular to the symmetry axis of the particle. For T7 an unexpectedly large increase of Δn_s and K_sp occurs at a glycerol concentration of about 30% (v/v). This increase is interpreted as being caused by a change of the shape of the particle and/or a change in the secondary structure of the DNA inside the head of the bacteriophage.     

Synthesis and characterization of thiolato-bridged cadmium(II) complexes with NNS-chelating thiolic ligands

Cadmium(II) complexes with 2-[(2-aminoethyl)amino]ethanethiol (HL¹), 2-[(3-aminopropyl)amino]ethanethiol (HL²), 2-[(2-pyridylmethyl)amino]ethanethiol (HL³), and 2-[[2-(2-pyridyl)ethyl]amino]ethanethiol (HL⁴), [Cd(L¹)](ClO₄) (1), [Cd(L²)](ClO₄)·1/2CH₃OH (2), [Cd{Cd(L²)₂}₂](ClO₄)₂·CH₃CON(CH₃)₂ (3a·CH₃CON(CH₃)₂), [Cd{Cd(L²)₂}₂]Cl₂·2CH₃OH (3b·2CH₃OH), [Cd{Cd(L³)₂}₂](ClO₄)₂ (4), [Cd(L⁴)](ClO₄) (5), have been synthesized and characterized by measurements of the infrared and electronic spectra. The X-ray crystal structures show that 3a and 3b have a thiolato-bridged trinuclear core with a linear arrangement of three metal atoms.     

Fluorescence emission mechanism and fluorescence properties of ternary Tb(III) complex with diphenyl sulphoxide and bipyridine

A novel ternary complex, TbL₅L′(ClO₄)₃·3H₂O, two binary complexes, TbL₇(ClO₄)₃·3H₂O and TbL′_3.5(ClO₄)₃·4H₂O has been synthesized (using diphenyl sulphoxide as the first ligand L, bipyridine as the second ligand L′). Their composition was analysed by element analysis, coordination titration, IR spectra and ¹H‐NMR, and the fluorescence emission mechanism, fluorescence intensities and phosphorescence spectra were also investigated by comparison. It was shown that the ternary rare‐earth complex showed stronger fluorescence intensities than the binary rare‐earth complexes in such material. The strongest characteristic fluorescence emission intensity of the ternary system was 8.23 times, 3.58 times as strong as that of the binary systems TbL₇(ClO₄)₃·3H₂O and TbL′_3.5 (ClO₄)₃·4H₂O, respectively. By fluorescence analysis it was found that both diphenyl sulphoxide and bipyridine could sensitize the fluorescence intensities of rare‐earth ions. In particular, in the ternary rare‐earth complex, introduction of bipyridine was of benefit to the fluorescence properties of Tb(III). Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of low-concentration chlorine dioxide gas against bacteria and viruses on a glass surface in wet environments

Aims: To evaluate the efficacy of low‐concentration chlorine dioxide (ClO₂) gas against model microbes in the wet state on a glass surface. Methods and Results: We set up a test room (39 m³) and the ClO₂ gas was produced by a ClO₂ gas generator that continuously releases a constant low‐concentration ClO₂ gas. Influenza A virus (Flu‐A), feline calicivirus (FCV), Staphylococcus aureus and Escherichia coli were chosen as the model microbes. The low‐concentration ClO₂ gas (mean 0·05 ppmv, 0·14 mg m^?3) inactivated Flu‐A and E. coli (>5 log₁₀ reductions) and FCV and S. aureus (>2 log₁₀ reductions) in the wet state on glass dishes within 5 h. Conclusions: The treatment of wet environments in the presence of human activity such as kitchens and bathrooms with the low‐concentration ClO₂ gas would be useful for reducing the risk of infection by bacteria and viruses residing on the environmental hard surfaces without adverse effects. Significance and Impact of the Study: This study demonstrates that the low‐concentration ClO₂ gas (mean 0·05 ppmv) inactivates various kinds of microbes such as Gram‐positive and Gram‐negative bacteria, enveloped and nonenveloped viruses in the wet state.