Quantitative evaluation of DNA damage and mutation rate by atmospheric and room-temperature plasma (ARTP) and conventional mutagenesis.

DNA damage is the dominant source of mutation, which is the driving force of evolution. Therefore, it is important to quantitatively analyze the DNA damage caused by different mutagenesis methods, the subsequent mutation rates, and their relationship. Atmospheric and room temperature plasma (ARTP) mutagenesis has been used for the mutation breeding of more than 40 microorganisms. However, ARTP mutagenesis has not been quantitatively compared with conventional mutation methods. In this study, the umu test using a flow-cytometric analysis was developed to quantify the DNA damage in individual viable cells using Salmonella typhimurium NM2009 as the model strain and to determine the mutation rate. The newly developed method was used to evaluate four different mutagenesis systems: a new ARTP tool, ultraviolet radiation, 4-nitroquinoline-1-oxide (4-NQO), and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) mutagenesis. The mutation rate was proportional to the corresponding SOS response induced by DNA damage. ARTP caused greater DNA damage to individual living cells than the other conventional mutagenesis methods, and the mutation rate was also higher. By quantitatively comparing the DNA damage and consequent mutation rate after different types of mutagenesis, we have shown that ARTP is a potentially powerful mutagenesis tool with which to improve the characteristics of microbial cell factories.

Theoretical study on the predissociation mechanism of CO(2)(+) (C (2)Sigma(g)(+)).

The main purpose of the present theoretical work was to study predissociation mechanism of the C (2)Sigma(g)(+) state of the CO(2)(+) ion using the CAS methods. Since the X (2)Pi(g), A (2)Pi(u), B (2)Sigma(u)(+), 1 (4)Sigma(g)(-), and 1 (4)Pi(u) states are involved in the predissociation, we also studied these five states. The CASPT2 calculations indicate that Renner-Teller splitting in 1 (4)Pi(u) leads to two C(2v) states, 1 (4)A(1) and 1 (4)B(1). For the X (2)Pi(g), A (2)Pi(u), B (2)Sigma(u)(+), and C (2)Sigma(g)(+) states, the CASPT2 T(0) values and geometries are in good agreement with experiment. The CASPT2 calculations for the O-loss dissociation potential energy curves indicate that the 1 (4)Sigma(g)(-), X (2)Pi(g), 1 (4)Pi(u), A (2)Pi(u), B (2)Sigma(u)(+), and C (2)Sigma(g)(+) states correlate with the first, second, second, third, third, and fourth dissociation limits, respectively. The CASSCF minimum energy crossing point (MECP) calculations (in the C(infinityv), C(s), and C(2v) symmetries) were performed for selected state/state pairs, and the spin-orbit couplings were calculated at the MECPs. All the MECPs (including the C (2)Sigma(g)(+)/1 (4)Pi(u) (1 (4)B(1)) MECP), involved in the proposed predissociation mechanism of Praet et al. ( J. Chem. Phys. 1982 , 77 , 4611 - 4618 ), were found and the calculated spin-orbit couplings at these MECPs are not small. Our calculations support the mechanism of Praet et al. and indicate that an energy value of 8.9 eV from CO(2)(+) (X (2)Pi(g)) is needed. The C (2)Sigma(g)(+) state in the previous [1 + 1] photodissociation experiments ( J. Chem. Phys. 2008 , 128 , 164308. ) could predissociate through the mechanism of Praet et al. since the two-photon energy was around 8.9 eV, while the C (2)Sigma(g)(+) state in the previous VUV-PFI-PE experiments ( J. Chem. Phys. 2003 , 118 , 149 - 163 ) would predissociate through another mechanism via A (2)Pi(u).

A theoretical study on the electronic states and O-loss photodissociation of the NO2(+) ion.

CASPT2 (multiconfiguration second-order perturbation theory) calculations were performed at the molecular geometry for 17 low-lying singlet and triplet states of the NO(2)(+) ion. The CASPT2 vertical relative energies (T(v)') were obtained and the characters of these ionic states (primary or shake-up ionization states) were determined. For the eight low-lying states, we performed CASPT2 geometry optimization calculations and obtained the CASPT2 adiabatic relative energies (T(0)). We conclude that the 1(1)A(1), 1(3)B(2), 1(3)A(2), 1(1)A(2), 1(1)B(2), 1(3)A(1), 2(3)B(1), and 3(3)B(2) states of NO(2)(+) correspond to the X(1)Sigma(g)(+), a(3)B(2), b(3)A(2), A(1)A(2), B(1)B(2), c(3)A(1), d(3)B(1), and (3b(2))(-1) (3)B(2) states (the eight ionic states below 20 eV observed in the photoelectron spectra of Brundle et al.1 and Baltzer et al.2), respectively. The 1(1)A(1), 1(3)B(2), 1(3)A(2), 1(1)A(2), 1(1)B(2), 1(3)A(1), and 3(3)B(2) states are primary ionization states, and the CASPT2 T(v)' and T(0) values of these states are close to the corresponding experimental values from refs. [1] and [2]. The 2(3)B(1) state is not a typical primary ionization state, and the CASPT2 T(v)' and T(0) values for 2(3)B(1) are in reasonable agreement with the experimental values for d(3)B(1) from refs. [1] and [2] (the CASPT2 T(0) value for 1(3)B(1) is more than 2.5 eV smaller than the experimental values). Based on our CASPT2 T(0) calculations, we comment on the assignments of the d(3)A(1), C(1)B(1), and D(1)B(2) states below 20 eV observed by Jarvis et al. and on the MRCI T(0) values of Hirst for the 1(3)B(1), 1(1)B(1), and (3)A(1) states. On the basis of the CASPT2 potential energy curve (PEC) and CASSCF singlet/triplet minimum-energy crossing point (MECP) calculations, we reach the following conclusions concerning O-loss photodissociation from the X(1)Sigma(g)(+), a(3)B(2), b(3)A(2), A(1)A(2), and B(1)B(2) states, which are in line with the experimental facts. The adiabatic dissociation process of the X(1)Sigma(g) (+) state to the second limit [NO(+)(X(1)Sigma(+))+O((1)D)] cannot occur due to a high energy barrier (>5.0 eV) along the PEC, and the nonadiabitic process of X(1)Sigma(g)(+) to the first limit [NO(+)(X(1)Sigma(+))+O((3)P)] via the triplet states is unlikely since the MECPs lie very high above X(1)Sigma(g)(+). For the a(3)B(2) and b(3)A(2) states, adiabatic dissociation processes to the first limit may occur. Both the A(1)A(2) and B(1)B(2) states can undergo processes of predissociation to the first limit by a repulsive 2(3)A'' state, since the MECPs lie low above A(1)A(2) and B(1)B(2) and the calculated spin-orbit couplings at the MECPs are not small.

Low-lying electronic states and Cl-loss photodissociation of the C2H3Cl+ ion studied using multiconfiguration second-order perturbation theory.

We studied the 1(2)A' '(X2A' '), 1(2)A' (A2A'), 2(2)A' ' (B2A' '), and 2(2)A' (C2A') states of the C2H3Cl+ ion using the complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) methods. For the four ionic states, we calculated the equilibrium geometries, adiabatic (T0) and vertical (Tv) excitation energies, and relative energies (Tv') at the geometry of the molecule at the CASPT2 level and the Cl-loss dissociation potential energy curves (PECs) at the CASPT2//CASSCF level. The computed oscillator strength f value for the X2A' ' <-- A2A' transition is very small, which is in line with the experimental fact that the A state has a long lifetime. The CASPT2 geometry and T0 value for the A2A' state are in good agreement with experiment. The CASPT2 Tv' values for the A2A', B2A' ', and C2A' states are in good agreement with experiment. The Cl-loss PEC calculations predict that the X2A' ', A2A', and C2A' states correlate to C2H3+ (XA1) and the BA' ' state to C2H3+ (1A' ') (the B2A' ' and C2A' PECs cross at R(C-Cl) approximately 2.24 A). Our calculations indicate that at 357 nm the X2A' ' state can undergo a transition to B2A' ' followed by a predissociation of B2A' ' by the repulsive C2A' state (via the B/C crossing), leading to C2H3+ (X1A1), and therefore confirm the experimentally proposed pathway for the photodissociation of X2A' ' at 357 nm. Our CASPT2 D0 calculations support the experimental fact that the X state does not undergo dissociation in the visible spectral region and imply that a direct dissociation of the A state to C2H3+ (X1A1) is energetically feasible.

Dissociation of the OCS+ ion in low-lying electronic states studied using multiconfiguration second-order perturbation theory.

Complete active space self-consistent-field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with atomic natural orbital basis sets were performed to investigate the S-loss direct dissociation of the 1 2Pi(X 2Pi), 2 2Pi(A 2Pi), 1 2Sigma+(B 2Sigma+), 1 4Sigma-, 1 2Sigma-, and 1 2Delta states of the OCS+ ion and the predissociations of the 1 2Pi, 2 2Pi, and 1 2Sigma+ states. Our calculations indicate that the S-loss dissociation products of the OCS(+) ion in the six states are the ground-state CO molecule plus the S+ ion in different electronic states. The CASPT2//CASSCF potential energy curves were calculated for the S-loss dissociation from the six states. The calculations indicate that the dissociation of the 1 4Sigma- state leads to the CO + S+ (4Su) products representing the first dissociation limit; the dissociations of the 1 2Pi, 1 2Sigma-, and 1 2Delta states lead to the CO + S+(2Du) products representing the second dissociation limit; and the dissociations of the 2 2Pi and 1 2Sigma+ states lead to the CO + S+(2Pu) products representing the third dissociation limit. Seams of the 1 2Pi-1 4Sigma-, 2 2Pi-1 4Sigma-, 2 2Pi-1 2Sigma-, 2 2Pi-1 2Delta, and 1 2Sigma(+)-1 4Sigma- potential energy surface intersections were calculated at the CASPT2 level, and the minima along the seams were located. The calculations indicate that within the experimental energy range (15.07-16.0 eV) the 2 2Pi(A 2Pi) state can be predissociated by 1 4Sigma- forming the S+(4Su) ion and can undergo internal conversion to 1 2Pi followed by the direct dissociation of 1 2Pi forming S+(2Du) and that within the experimental energy range (16.04-16.54 eV) the 1 2Sigma+(B 2Sigma+) state can be predissociated by 1 4Sigma- forming the S+(4Su) ion and can undergo internal conversion to 2 2Pi followed by the predissociation of 2 2Pi by 1 2Sigma- and 1 2Delta forming the S+(2Du) ion. These indications are in line with the experimental fact that both the 4Su and 2Du states of the S+ ion can be formed from the 2 2Pi and 1 2Sigma+ states of the OCS+ ion.

Electroanalytical method for TPPS4, the interaction of TPPS4 with BSA and the influence of CDs on it by fluorescence spectroscopy.

AIM: To establish a simple, rapid and accurate electroanalytical method for water soluble porphyrin meso-tetrakis-(4-sulfonatophenyl) porphyrin (TPPS4); to clarify the reaction between water soluble porphyrins and bovine serum albumin (BSA); and to determine the interaction of TPPS4 with BSA in the absence of presence of cyclodextrins (CDs), separately. METHODS: Three methods including LSV, UV spectroscopy and fluorescence spectroscopy had been employed to the relevant experiments. The way of employing three methods at the same time could make the experiment results more reliable. RESULTS: In the supporting electrolyte of NaH2 PO4-Na2 HPO4 (pH 7.18), a sensitive reduction peak of TPPS4 was found by linear sweep voltammetry (LSV), the peak potential (Ep) was -0.70 V (vs SCE). The relationship between the second derivative peak of LSV (ip") and the concentration of TPPS4 was linear from 1.0 x 10(-7) mol x L(-1) to 1.0 x 10(-5) mol x L(-1), the square of correlation coefficients (r2) were 0.998 3 and 0.999 3, respectively. The relative standard deviation (RSD) was 0.56% (n = 5). The mean recovery of TPPS4 was 99.59%. In NH4Cl-NH3 x H2O buffers (pH 9.05), it was proved that BSA and TPPS4 could interact with each other and form 1 : 1 TPPS4-BSA supramolecular system. Moreover, the interaction between TPPS4 and BSA had been investigated by adding cyclodextrins (CDs). The interaction of TPPS4 with BSA was facilitated both by hydroxypropyl-beta-CD (HP-beta-CD) and sulforbutylether-beta-CD (SBE-beta-CD). CONCLUSION: An electroanalytical method for TPPS4 has been established by LSV. The porphyrin drugs included by CDs could react with protein existing inside the human body easier. The consequences of this article also show that CDs will play important role in controlling and releasing the porphyrin drugs.