Adaptive Dynamics Simulation of Interference Phenomenon for Physical and Biological Systems.

Biological systems have been shown to have quantum-like behaviors by applying the adaptive dynamics view on their interaction networks. In particular, in the process of lactose-glucose metabolism, cells generate probabilistic interference patterns similarly to photons in the two-slit experiment. Such quantum-like interference patterns can be found in biological data, on all scales, from proteins to cognitive, ecological, and social systems. The adaptive dynamics approach covers both biological and physical phenomena, including the ones which are typically associated with quantum physics. We guess that the adaptive dynamics can be used for the clarification of quantum foundations, and the present paper is the first step in this direction. We suggest the use of an algorithm for the numerical simulation of the behavior of a billiard ball-like particle passing through two slits by explicitly considering the influence of the two-slit environment (experimental context). Our simulation successfully mimics the interference pattern obtained experimentally in quantum physics. The interference of photons or electrons by two slits is known as a typical quantum mechanical effect. We do not claim that the adaptive dynamics can reproduce the whole body of quantum mechanics, but we hope that this numerical simulation example will stimulate further extensive studies in this direction-the representation of quantum physical phenomena in an adaptive dynamical framework.

An affinity change model to elucidate the rotation mechanism of V1-ATPase.

V-ATPases are ubiquitous proton-transporting ATPases of eukaryotic and prokaryotic membranes that utilize energy from ATP hydrolysis. The hydrophilic catalytic part called V1-ATPase is composed of a ring-shaped hexametric A3B3 complex and a central DF shaft. We previously proposed a rotation mechanism of the Enterococcus hirae V1-ATPase based on the crystal structures of the V1 and A3B3 complexes. However, the driving force that induces the conformational changes of A3B3 and rotation of the DF shaft remains unclear. In this study, we investigated the binding affinity changes between subunits of V1-ATPase by surface plasmon resonance analysis. The binding of ATP to subunit A was found to considerably increase the affinity between the A and B subunits, and thereby ATP binding contributes to forming the A1B1 tight conformation. Furthermore, the DF shaft bound to the reconstituted A1B1 complex with high affinity, suggesting that the tight A1B1 complex is a major binding unit of the shaft in the A3B3 ring complex. Based on these results, we propose that rotation of the V1-ATPase is driven by affinity changes between each subunit via thermal fluctuations.

Rotation mechanism of Enterococcus hirae V1-ATPase based on asymmetric crystal structures.

In various cellular membrane systems, vacuolar ATPases (V-ATPases) function as proton pumps, which are involved in many processes such as bone resorption and cancer metastasis, and these membrane proteins represent attractive drug targets for osteoporosis and cancer. The hydrophilic V(1) portion is known as a rotary motor, in which a central axis DF complex rotates inside a hexagonally arranged catalytic A(3)B(3) complex using ATP hydrolysis energy, but the molecular mechanism is not well defined owing to a lack of high-resolution structural information. We previously reported on the in vitro expression, purification and reconstitution of Enterococcus hirae V(1)-ATPase from the A(3)B(3) and DF complexes. Here we report the asymmetric structures of the nucleotide-free (2.8 Å) and nucleotide-bound (3.4 Å) A(3)B(3) complex that demonstrate conformational changes induced by nucleotide binding, suggesting a binding order in the right-handed rotational orientation in a cooperative manner. The crystal structures of the nucleotide-free (2.2 Å) and nucleotide-bound (2.7 Å) V(1)-ATPase are also reported. The more tightly packed nucleotide-binding site seems to be induced by DF binding, and ATP hydrolysis seems to be stimulated by the approach of a conserved arginine residue. To our knowledge, these asymmetric structures represent the first high-resolution view of the rotational mechanism of V(1)-ATPase.

Rotation Mechanism of Molecular Motor V1-ATPase Studied by Multiscale Molecular Dynamics Simulation.

Enterococcus hirae V1-ATPase is a molecular motor composed of the A3B3 hexamer ring and the central stalk. In association with ATP hydrolysis, three catalytic AB pairs in the A3B3 ring undergo conformational changes, which lead to a 120° rotation of the central stalk. To understand how the conformational changes of three catalytic pairs induce the 120° rotation of the central stalk, we performed multiscale molecular dynamics (MD) simulations in which coarse-grained and all-atom MD simulations were combined using a fluctuation matching methodology. During the rotation, a catalytic AB pair spontaneously adopted an intermediate conformation, which was not included in the initial inputs of the simulations and was essentially close to the "bindable-like" structure observed in a recently solved crystal structure. Furthermore, the creation of a space between the bindable-like and tight pairs was required for the central stalk to rotate without steric hindrance. These cooperative rearrangements of the three catalytic pairs are crucial for the rotation of the central stalk.

Intraarterial Therapy Using Micellar Nanoparticles Incorporating SN-38 in a Rabbit Liver Tumor Model.

PURPOSE: To evaluate the pharmacokinetics of intraarterial (IA) administration of micellar nanoparticles incorporating SN-38 injection compared with intravenous (IV) administration in a rabbit liver tumor model. MATERIALS AND METHODS: In this animal care committee-approved study, 18 rabbits (mean weight, 3.89 kg; range, 3.20-4.70 kg) with VX2 liver tumors were divided into two groups (IA and IV). Micellar nanoparticles incorporating SN-38 (30 mg/kg) were injected through the left hepatic artery in the IA group and the right femoral vein in the IV group. NK012 and free SN-38 in the plasma, liver parenchyma, and tumors were measured within 24 hours. Histologic examinations were conducted at 2 and 24 hours. RESULTS: There were no significant differences in the serum area under the concentration-time curve (0-24 h) for free SN-38, at 1,500 and 1,310 µg∙min/mL in the IA and IV groups, respectively (P = .152). The IA group showed significantly higher free SN-38 concentrations in tumor tissues at all time points compared with the IV group (P = .002 at 3 min, P = .011 at 2 h, and P = .047 at 24 h). Histologic findings showed that significantly higher tumor necrosis ratios were observed in the IA group compared with the IV group at 24 hours (P = .028). CONCLUSIONS: Micellar nanoparticles could be a promising IA drug delivery system to achieve high tumor tissue concentrations of SN-38.

The Administration of Celecoxib as an Analgesic after Liver Resection Is Safe.

BACKGROUND: There are a few studies that have evaluated postoperative analgesia. The aim of this study was to evaluate the safety of administering celecoxib to manage postoperative pain after liver surgery. METHODS: The cases of patients who underwent liver resection at Nara Medical University from April 2008 to December 2015 were retrospectively analyzed. From January 2013 to December 2015, celecoxib was routinely administered (600 mg/day on postoperative day (POD) 2 and 400 mg/day from POD 3-7), whereas celecoxib was not administered from April 2008 to December 2012. The patients' baseline characteristics, the operative procedures, and postoperative complications were analyzed. RESULTS: In total, 207 patients were administered celecoxib (celecoxib group), whereas 246 were not (non-celecoxib group). The preoperative serum total bilirubin and creatinine levels and indocyanine green retention rate at 15 min values of the 2 groups were similar. Similar incidences of overall and major complications (Clavien-Dindo classification ≥grade IIIa) were seen in both groups (33.8 vs. 36.2%, p = 0.601 and 12.1 vs. 12.6%, p = 0.866, respectively). No significant differences in the incidences of gastrointestinal bleeding, acute renal failure, or portal vein thrombosis were observed between the groups. CONCLUSIONS: The use of celecoxib for postoperative analgesia in the early period after liver resection is safe.

The prognosis of liver resection for patients with four or more colorectal liver metastases has not improved in the era of modern chemotherapy.

BACKGROUND AND OBJECTIVES: The impact of perioperative chemotherapy on patients with multiple colorectal liver metastases (CRLM) remains unclear. We attempted to examine whether the introduction of modern chemotherapies has improved the prognosis of patients that undergo liver resection for ≥4 CRLM. METHODS: Between January 1990 and December 2013, 194 patients underwent liver resection for CRLM at our institution. The outcomes of the patients with ≥4 and 1-3 CRLM were compared before and after 2005, when modern chemotherapies were introduced to Japan. RESULTS: There were 50 and 144 patients with ≥4 (Group 1) and 1-3 (Group 2) CRLM, respectively. The overall survival (OS) rate of Group 1 was significantly worse than that of Group 2 (P = 0.0007). The OS rate of Group 2 was significantly better after 2005 than before 2004 (P = 0.039), while no such differences were observed in Group 1. Multivariate analysis identified three prognostic factors in Group 1: a serum carcinoembryonic antigen level of ≥20 ng/ml (P = 0.018), a serum cancer antigen 19-9 level of ≥100 U/ml (P = 0.018), and a primary colorectal cancer N factor of ≥N2 (P = 0.023). CONCLUSIONS: The prognosis of patients with ≥4 CRLM that undergo liver resection has not improved despite the development of modern chemotherapies. J. Surg. Oncol. 2016;114:959-965. © 2016 Wiley Periodicals, Inc.

Binding interactions of the peripheral stalk subunit isoforms from human V-ATPase.

The mammalian peripheral stalk subunits of the vacuolar-type H(+)-ATPases (V-ATPases) possess several isoforms (C1, C2, E1, E2, G1, G2, G3, a1, a2, a3, and a4), which may play significant role in regulating ATPase assembly and disassembly in different tissues. To better understand the structure and function of V-ATPase, we expressed and purified several isoforms of the human V-ATPase peripheral stalk: E1G1, E1G2, E1G3, E2G1, E2G2, E2G3, C1, C2, H, a1NT, and a2NT. Here, we investigated and characterized the isoforms of the peripheral stalk region of human V-ATPase with respect to their affinity and kinetics in different combination. We found that different isoforms interacted in a similar manner with the isoforms of other subunits. The differences in binding affinities among isoforms were minor from our in vitro studies. However, such minor differences from the binding interaction among isoforms might provide valuable information for the future structural-functional studies of this holoenzyme.

Impact of Mechanical Bowel Preparation on Postoperative Outcomes after Liver Resection for Patients with Hepatocellular Carcinoma: A Single-Center Retrospective Cohort Study.

BACKGROUND: Despite the routine use of mechanical bowel preparation (MBP), the real impact of MBP for liver resection remains unclear. The aim of this study was to evaluate the postoperative outcomes of MBP after liver resection for hepatocellular carcinoma (HCC). METHODS: This was a retrospective cohort study of all patients undergoing liver resection for patients with HCC between from April 2008 to March 2015. MBP was defined as a preoperative medication of polyethylene glycol lavage. We compared perioperative outcomes in patients who did or did not receive MBP before liver resection. Open and laparoscopic hepatectomy were analyzed separately. RESULTS: A total of 227 patients underwent potentially curative liver resection for HCC during the study period. One hundred twenty-eight patients received MBP while 99 did not. In the open hepatectomy group, overall and major (Clavien-Dindo ≥3) complications were equivalent between the groups (31.9 vs. 25.8%, p = 0.840; 12.1 vs. 8.7%, p = 0.475). There were no meaningful differences in the incidence of liver failure (MBP: 22.4%, non-MBP: 13.0%, p = 0.116). Surgical-site infections occurred in 20 (17.2%) vs. 10 (14.5%) with no significant difference (p = 0.624). Similar results were obtained from the laparoscopic hepatectomy group. CONCLUSION: The use of MBP does not appear to impact the short outcomes after liver resection for patients with HCC. MBP might be omitted in liver surgery.

[Long-Term Survival in a Case of Sigmoid Colon Cancer with Multiple Liver Metastases Treated with Repeated Hepatectomies].

A 75-year-old man was diagnosed with sigmoid colon cancer with multiple liver metastases at our hospital in May 2010. He underwent mFOLFOX6 and panitumumab chemotherapy for 6 months. He then underwent sigmoidectomy, lymphadenectomy D3, partial resection of 2 parts of S6, and cholecystectomy in January 2011. However, he underwent partial resection of the liver an additional 4 times in the 5 years followingthe primary operation. Despite multiple liver metastases, he is alive 5 years after the primary operation, havingsurvived 5 hepatectomies for multiple resectable liver metastases.

Torque generation of Enterococcus hirae V-ATPase.

V-ATPase (V(o)V1) converts the chemical free energy of ATP into an ion-motive force across the cell membrane via mechanical rotation. This energy conversion requires proper interactions between the rotor and stator in V(o)V1 for tight coupling among chemical reaction, torque generation, and ion transport. We developed an Escherichia coli expression system for Enterococcus hirae V(o)V1 (EhV(o)V1) and established a single-molecule rotation assay to measure the torque generated. Recombinant and native EhV(o)V1 exhibited almost identical dependence of ATP hydrolysis activity on sodium ion and ATP concentrations, indicating their functional equivalence. In a single-molecule rotation assay with a low load probe at high ATP concentration, EhV(o)V1 only showed the "clear" state without apparent backward steps, whereas EhV1 showed two states, "clear" and "unclear." Furthermore, EhV(o)V1 showed slower rotation than EhV1 without the three distinct pauses separated by 120° that were observed in EhV1. When using a large probe, EhV(o)V1 showed faster rotation than EhV1, and the torque of EhV(o)V1 estimated from the continuous rotation was nearly double that of EhV1. On the other hand, stepping torque of EhV1 in the clear state was comparable with that of EhV(o)V1. These results indicate that rotor-stator interactions of the V(o) moiety and/or sodium ion transport limit the rotation driven by the V1 moiety, and the rotor-stator interactions in EhV(o)V1 are stabilized by two peripheral stalks to generate a larger torque than that of isolated EhV1. However, the torque value was substantially lower than that of other rotary ATPases, implying the low energy conversion efficiency of EhV(o)V1.

Eosinophilic cholangitis coexisted with idiopathic thrombocytopenic purpura: Report of a case.

Eosinophilic cholangitis is a rare disease of which only 31 cases have been reported. Eosinophilic infiltration causes stricture of the bile duct diffusely or locally, and the imaging of eosinophilic cholangitis resembles primary sclerosing cholangitis or cancer of the bile tract. For eosinophilic cholangitis, treatment with steroid is effective and the prognosis is good. Therefore, its accurate diagnosis is very important. Here, we describe a patient with eosinophilic cholangitis who was also diagnosed with idiopathic thrombocytopenic purpura (ITP). He was treated for ITP using prednisolone, the unexpected sudden interruption of which caused severe deterioration of eosinophilic cholangitis and acute cholecystitis. Cholecystectomy and choledochojejunostomy were performed, and the addition of treatment by prednisolone resulted in a good clinical course. This is the first report on eosinophilic cholangitis coexisting with ITP.

Basic properties of rotary dynamics of the molecular motor Enterococcus hirae V1-ATPase.

V-ATPases are rotary molecular motors that generally function as proton pumps. We recently solved the crystal structures of the V1 moiety of Enterococcus hirae V-ATPase (EhV1) and proposed a model for its rotation mechanism. Here, we characterized the rotary dynamics of EhV1 using single-molecule analysis employing a load-free probe. EhV1 rotated in a counterclockwise direction, exhibiting two distinct rotational states, namely clear and unclear, suggesting unstable interactions between the rotor and stator. The clear state was analyzed in detail to obtain kinetic parameters. The rotation rates obeyed Michaelis-Menten kinetics with a maximal rotation rate (Vmax) of 107 revolutions/s and a Michaelis constant (Km) of 154 µM at 26 °C. At all ATP concentrations tested, EhV1 showed only three pauses separated by 120°/turn, and no substeps were resolved, as was the case with Thermus thermophilus V1-ATPase (TtV1). At 10 µM ATP (<>Km), the distribution of the durations of the catalytic pause was reproduced by a consecutive reaction with two time constants of 2.6 and 0.5 ms. These kinetic parameters were similar to those of TtV1. Our results identify the common properties of rotary catalysis of V1-ATPases that are distinct from those of F1-ATPases and will further our understanding of the general mechanisms of rotary molecular motors.

Significant involvement of herpesvirus entry mediator in human esophageal squamous cell carcinoma.

BACKGROUND: Herpesvirus entry mediator (HVEM) is known to regulate immune response and to be expressed in several human malignancies. However, to the authors's knowledge, the precise role of HVEM in human cancer biology remains unknown. The objective of the current study was to clarify the clinical significance of HVEM in human esophageal squamous cell carcinoma as well as its in vivo functions. METHODS: HVEM expression was evaluated in 103 patients with esophageal squamous cell carcinoma to explore its clinical relevance and prognostic value. The functions of HVEM in tumors were analyzed in vitro and in vivo using the small interfering RNA (siRNA) silencing technique. RESULTS: HVEM expression was found to be significantly correlated with depth of tumor invasion and lymph node metastasis. Furthermore, it was found to be inversely correlated with tumor-infiltrating CD4(+) , CD8(+) , and CD45RO(+) lymphocytes. It is important to note that HVEM status was identified as an independent prognostic marker. HVEM gene silencing significantly inhibited cancer cell proliferation in vitro and cancer growth in vivo. This antitumor effect was associated with reduced cell proliferation activity. The effect was also correlated with the induction of CD8(+) cells and upregulation of local immune response. CONCLUSIONS: HVEM plays a critical role in both tumor progression and the evasion of host antitumor immune responses, possibly through direct and indirect mechanisms. Therefore, HVEM may be a promising therapeutic target for human esophageal cancer.

Structure of the rotor ring modified with N,N'-dicyclohexylcarbodiimide of the Na+-transporting vacuolar ATPase.

The prokaryotic V-ATPase of Enterococcus hirae, closely related to the eukaryotic enzymes, provides a unique opportunity to study the ion-translocation mechanism because it transports Na(+), which can be detected by radioisotope (22Na(+)) experiments and X-ray crystallography. In this study, we demonstrated that the binding affinity of the rotor ring (K ring) for 22Na(+) decreased approximately 30-fold by reaction with N,N(')-dicyclohexylcarbodiimide (DCCD), and determined the crystal structures of Na(+)-bound and Na(+)-unbound K rings modified with DCCD at 2.4- and 3.1-Å resolutions, respectively. Overall these structures were similar, indicating that there is no global conformational change associated with release of Na(+) from the DCCD-K ring. A conserved glutamate residue (E139) within all 10 ion-binding pockets of the K ring was neutralized by modification with DCCD, and formed an "open" conformation by losing hydrogen bonds with the Y68 and T64 side chains, resulting in low affinity for Na(+). This open conformation is likely to be comparable to that of neutralized E139 forming a salt bridge with the conserved arginine of the stator during the ion-translocation process. Based on these findings, we proposed the ion-translocation model that the binding affinity for Na(+) decreases due to the neutralization of E139, thus releasing bound Na(+), and that the structures of Na(+)-bound and Na(+)-unbound DCCD-K rings are corresponding to intermediate states before and after release of Na(+) during rotational catalysis of V-ATPase, respectively.

Crystal structure of the central axis DF complex of the prokaryotic V-ATPase.

V-ATPases function as ATP-dependent ion pumps in various membrane systems of living organisms. ATP hydrolysis causes rotation of the central rotor complex, which is composed of the central axis D subunit and a membrane c ring that are connected by F and d subunits. Here we determined the crystal structure of the DF complex of the prokaryotic V-ATPase of Enterococcus hirae at 2.0-Å resolution. The structure of the D subunit comprised a long left-handed coiled coil with a unique short ß-hairpin region that is effective in stimulating the ATPase activity of V(1)-ATPase by twofold. The F subunit is bound to the middle portion of the D subunit. The C-terminal helix of the F subunit, which was believed to function as a regulatory region by extending into the catalytic A(3)B(3) complex, contributes to tight binding to the D subunit by forming a three-helix bundle. Both D and F subunits are necessary to bind the d subunit that links to the c ring. From these findings, we modeled the entire rotor complex (DFdc ring) of V-ATPase.

Postoperative outcomes of patients with hepatocellular carcinoma negative for all virus-related markers.

PURPOSE: The outcomes of patients with resectable hepatocellular carcinoma (HCC) negative for all virus-related markers have not yet been characterized. This study investigated the outcomes of such patients in comparison to those who had virus-related resectable HCC. METHODS: A total of 398 patients with HCC were divided into 2 groups, comprising patients in which all virus-related markers (HBs-Ag, HBs-Ab, HBe-Ag, HBe-Ab, HBc-Ab, HCV-Ab) were negative (all-negative group, n = 63) and those with at least 1 positive virus-related marker (virus-related group, n = 335). The clinical characteristics, surgical data, and survival rates were compared between the groups. RESULTS: The serum AST (30 vs. 45 IU/l, P < 0.0001) and ALT (21 vs. 42 IU/l, P < 0.0001) levels were significantly lower in the all-negative group than in the virus-related group. The tumor size (4.3 vs. 3.1 cm, P < 0.0001), the prevalence of DM (46.8 vs. 25.4 %, P = 0.001), and BMI (24.8 vs. 22.9, P = 0.0023) were significantly higher in the all-negative group than in the virus-related group. HCC arose from a cirrhotic liver in a significantly higher proportion of patients in the virus-related group than in the all-negative group (20.6 vs. 44.8 %, P = 0.0002). The survival outcomes were not significantly different in the 2 groups (all-negative vs. virus-related: 5-year overall survival rate, 58.2 vs. 55.2 %, P = 0.27), despite such differences in the patients' characteristics. CONCLUSIONS: The postoperative outcomes of patients with HCC are independent of the presence or absence of hepatitis viral infection.

Acute peritonitis caused by the acute pancreatitis of an ectopic pancreas in a jejunal duplication, in an adult with intestinal malrotation: a case report.

BACKGROUND: Intestinal duplication and ectopic pancreas are two rare independent congenital anomalies. Few reports describe cases of patients with ectopic pancreas in an intestinal duplication causing acute peritonitis. CASE PRESENTATION: A 31-year-old man was admitted to the hospital for epigastric pain. The patient was diagnosed with acute peritonitis caused by the acute pancreatitis of an ectopic pancreas in a jejunal duplication, with intestinal malrotation. The patient underwent the partial resection of the jejunum and Ladd's procedure. The histopathological findings indicated ectopic pancreatitis in the jejunal duplication. CONCLUSIONS: We presented the case of acute peritonitis caused by the acute pancreatitis of an ectopic pancreas in a jejunal duplication in an adult with intestinal malrotation. Surgery is the primary treatment and is necessary for a definitive diagnosis.

Mutagenesis of the residues forming an ion binding pocket of the NtpK subunit of Enterococcus hirae V-ATPase.

The crystal structures of the Na(+)- and Li(+)-bound NtpK rings of Enterococcus hirae V-ATPase have been obtained. The coupling ion (Na(+) or Li(+)) was surrounded by five oxygen atoms contributed by residues T64, Q65, Q110, E139, and L61, and the hydrogen bonds of the side chains of Q110, Y68, and T64 stabilized the position of the E139 γ carboxylate essential for ion occlusion (PDB accession numbers 2BL2 and 2CYD). We previously indicated that an NtpK mutant strain (E139D) lost tolerance to sodium but not to lithium at alkaline pHs and suggested that the E139 residue is indispensable for the enzymatic activity of E. hirae V-ATPase linked with the sodium tolerance of this bacterium. In this study, we examined the activities of V-ATPase in which these four residues, except for E139, were substituted. The V-ATPase activities of the Q65A and Y68A mutants were slightly retained, but those of the T64A and Q110A mutants were negligible. Among the residues, T64 and Q110 are indispensable for the ion coupling of E. hirae V-ATPase, in addition to the essential residue E139.

Potent inhibition of dinuclear zinc(II) peptidase, an aminopeptidase from Aeromonas proteolytica, by 8-quinolinol derivatives: inhibitor design based on Zn2+ fluorophores, kinetic, and X-ray crystallographic study.

The selective inhibition of an aminopeptidase from Aeromonas proteolytica (AAP), a dinuclear Zn(2+) hydrolase, by 8-quinolinol (8-hydroxyquinoline, 8-HQ) derivatives is reported. We previously reported on the preparation of 8-HQ-pendant cyclens as Zn(2+) fluorophores (cyclen is 1,4,7,10-tetraazacyclododecane), in which the nitrogen and phenolate of the 8-HQ units (as well as the four nitrogens of cyclen) bind to Zn(2+) in a bidentate manner to form very stable Zn(2+) complexes at neutral pH (K (d) = 8-50 fM at pH 7.4). On the basis of this finding, it was hypothesized that 8-HQ derivatives have the potential to function as specific inhibitors of Zn(2+) enzymes, especially dinuclear Zn(2+) hydrolases. Assays of 8-HQ derivatives as inhibitors were performed against commercially available dinuclear Zn(2+) enzymes such as AAP and alkaline phosphatase. 8-HQ and the 5-substituted 8-HQ derivatives were found to be competitive inhibitors of AAP with inhibition constants of 0.16-29 µM at pH 8.0. The nitrogen at the 1-position and the hydroxide at the 8-position of 8-HQ were found to be essential for the inhibition of AAP. Fluorescence titrations of these drugs with AAP and an X-ray crystal structure analysis of an AAP-8-HQ complex (1.3-Å resolution) confirmed that 8-HQ binds to AAP in the "Pyr-out" mode, in which the hydroxide anion of 8-HQ bridges two Zn(2+) ions (Zn1 and Zn2) in the active site of AAP and the nitrogen atom of 8-HQ coordinates to Zn1 (Protein Data Bank code 3VH9).