Response of an allergenic species, Ambrosia psilostachya (Asteraceae), to experimental warming and clipping: implications for public health

We examined the responses of an allergenic species, western ragweed (Ambrosia psilostachya DC.), to experimental warming and clipping. The experiment was conducted in a tallgrass prairie in Oklahoma, USA, between 1999 and 2001. Warming increased ragweed stems by 88% when not clipped and 46% when clipped. Clipping increased ragweed stems by 75% and 36% in the control and warmed plots, respectively. In 2001, warming resulted in a 105% increase in ragweed aboveground biomass (AGB), and the ratio of ragweed AGB to total AGB increased by 79%. Dry mass per ragweed stem in the warmed plots was 37% and 38% greater than that in the control plots in 2000 and 2001, respectively. Although warming caused no difference in pollen production per stem, total pollen production increased by 84% (P < 0.05) because there were more ragweed stems. Experimental warming significantly increased pollen diameter from 21.2 μm in the control plots to 23.9 μm in the warmed plots (a 13% increase). The results from our experiment suggest that global warming could aggravate allergic hazards and thereby jeopardize public health.

Characterization of T-ray binary lenses

Multilevel phase-shift Fresnel diffractive zone plates fabricated on silicon wafers have been used as T-ray imaging lenses. The imaging results, including spatial and temporal distribution of T-rays measured at the focal planes in the frequency range from 0.5 to 1.5 THz, indicate that the performance of the diffractive terahertz (THz) lens is comparable with or better than that of conventional refractive THz lenses. The unique properties of the T-ray binary lens make it possible to fabricate excellent optics for narrow-band THz applications.

[Field study on the removal of arsenic from dispersed drinking water]

Shanyin county, an area prevalent of endemic arsenic poisoning in Shanxi Province, was selected as the experimental field to verify the methods studied for removal arsenic from dispersed drinking water. The results showed that the desired goal has been achieved from the field study. The results confirmed that arsenate could be removed from drinking water by using ferric sulfate or aluminum sulfate as coagulants and employing sand filtration. Javelle water(sodium hypochlorite) is an effective oxidant for arsenite. The performance of iron oxide-coated sand developed in this study was good for arsenic removal. Further study and application is needed.

[Expression of CD44V6 in squamous cell carcinoma of the lung]

BACKGROUND

To study the expression of CD44V6 in squamous cell carcinoma of the lung ( SCC) and the correlation between the CD44V6 positive expression and the carcinogenesis and development of SCC.

METHODS

Using immunohistochemistry avidin biotin peroxidase complex ( ABC) method, CD44V6 protein expression was detected in the fresh cancer tissues and normal tissues adjacent to cancer from 35 patients with SCC.

RESULTS

CD44V6 presented high expression in cancer tissues ( 65. 7%, 23/ 35) , but it was not detected in the normal tissues adjacent to cancer (Chi-square = 34. 3, P < 0. 01) ; compared with SCC without lymph node metastasis ( CD44V6 positive rate was 43. 8%, 7/ 16) , SCC with lymph node metastasis showed strong expression of CD44V6 ( 84. 2%, 16/ 19) (Chi-square = 6. 3, P < 0. 01) . CD44V6 expression increased with the cell differentiation of tumor decreasing, but with no statistic significance (Chi-square = 2. 33, P > 0. 05) . There was a distinct difference in CD44V6 expression between stage I + II ( 50%, 10/ 20) and stage III + IV ( 86. 7%, 13/15) (Chi-square= 5. 1, P < 0. 01) with a tendency of higher stage with higher expression of CD44V6. The 3-year survival rate in patients with CD44V6 positive expression ( 30. 4%, 7/ 23) was significantly lower than that in patients without CD44V6 expression ( 66. 7%, 8/ 12) (Chi-square = 4. 2, P < 0. 05) .

CONCLUSIONS

The results suggest that CD44V6 may play an important role in the carcinogenesis and the development of SCC and that routine assessment of CD44V6 expression may be valuable for deciding TNM stage of SCC. CD44V6 is considered as an indicator of prognosis for patients with SCC of the lung .

[Removal of arsenic from dispersed drinking water by iron oxide-coated sand]

The iron oxide-coated sand(IOCS) was developed by treating normal river sand with molysite and investigated by batch, column tests and autoptic experiment to evaluate it's ability of eliminating arsenic from dispersed drinking water. The results showed that IOCS was relatively stable and can be seen iron oxide distributedly patched the surface of sand by scan electron microscope. IOCS needn't any activation pretreatment. It reached the maximum adsorption within 30-60 min. The removal percentage of arsenate was decreased but the one of arsenite had little change when the pH varied from 5 to 9. And the arsenic adsorption matched the Langmuir isotherm. In 5 circles of runs, it treated 408-426 (arsenite) beds and 390-412(arsenate) beds volume of water with 75 g(50 ml) IOCS respectively when the influent arsenic concentration was 1.0 mg.L-1. And the arsenic percentage recovery was above 94% when regenerating the IOCS by 0.2 mol.L-1 NaOH. The home simulation unit contained IOCS 3.0 kg produced 209 L and 198 L, 196 L and 185 L of water when the influent arsenate or arsenite concentration was 1.0 mg.L-1, and 200 L arsenic free water with the influent arsenic 0.202-1.733 mg.L-1 during the field experimental period. The water quality was not affected by the adsorbent. With low-cost and simple operation, the IOCS should be a promising novel medium for arsenic removal in dispersed drinking water.

[Factors affecting arsenic removal with copolymer coagulant and their mechanism]

The removal of arsenic from drinking water with copolymer coagulant was investigated. The effect of the component, additive substance of the coagulant and filtration were tested by employing a orthogonal analysis. The results showed that the arsenic removal with ferric sulfate was better than that with ferric-aluminum copolymer and polysilicon metal salt. Adding active carbon powder or kaoline could not enhance the efficacy of arsenic removal. However, the removal rate was improved by filtration after using coagulates, and sand filtration was feasible. The efficacy of arsenic removal could be affected by the column height filled with sand and the diameter of sand. After arsenic adsorption model fitted, the Lang-muire isotherm was matched. The main mechanism of arsenic removal by coagulation should be adsorption.

[Purification and properties of neutral phytase form Bacillus subtilis]

A strain Bacillus subtilis producing neutral phytase was screened from soil. The protein of phytase was purified by HPLC. Optimal pH value and temperature of the phytase for its activity were 7.5 and 55 degrees C, respectively. The Km values of the phytase for dodecasodium phytate under 37 degrees C was 0.19 mmol/L. The molecule weight of the phytase protein was determined as about 45 kD by SDS-PAGE. The N-terminal amino acids sequence of the phytase protein was determined as Lys-His-Lys-Leu-Ser-Asp-Pro-Tyr-His-Phe-Thr by amino acids sequence analysis.

[Effect of fetal spinal cord graft with nerve growth factor and nimodipine in secondary injury of spinal cord of adult rat]

OBJECTIVE

To observe the effect of nerve growth factor (NGF) and nimodipine (NP) on fetal spinal cord graft in repair of injury of spinal cord.

METHODS

A total of 144 adult Wistar rats were included in this study. All were made as the hemi-section cavity injury model at the lumbar enlargement and divided into three groups: fetal spinal cord graft (group Tr), fetal spinal cord graft with NGF (group TN), and fetal spinal cord graft with NGF and NP (group TNN). The intracellular concentration of free ionic calcium was measured at the 4th, 8th, and 24th hour, and superoxidase (SOD) and malondialdehyde (MDA) at 3rd, 6th, 12th, 24th and 72nd hour after operation.

RESULTS

After spinal cord was injured, the concentration of MDA and intracellular concentration of free ionic calcium increased and reached to the peak at the 6th and 8th hour respectively, but SOD decreased and at 24th hour to its vale. The MDA was significantly lower in group TN than in group Tr, while the SOD was higher (P < 0.05). There was no significant difference on intracellular free ionic calcium concentration between group Tr and TN. The concentration of SOD of group TNN was the highest and the intracellular concentration of free ionic calcium was the lowest in the three groups (P < 0.05). The weekly mortality was 33%, 31%, 17% respectively in group Tr, TN and TNN. The mortality of group TNN was significantly lower than the other two groups (P < 0.01).

CONCLUSION

Although the fetal spinal cord graft is an effective method to repair laboratory spinal cord injury, NGF and ND can interrupt secondary injury and increase survival rate of the host.

[Study on the removal of arsenite from dispersed drinking water]

The feasible methods for oxidation and removal of arsenite[As(III)] from dispersed drinking water were based on the removal of arsenate[As(V)] by ferric sulfate. The results showed that the spotaneous oxidation of As(III) to As(V) was very slow and could not be enhanced by aerating for 24 h. The removal rate of As(III) could reach that of As(V) when pre-aerating water samples with ozone for 60 s, putting 7.5 ml/L hydrogen peroxide solution, adding 2.5 mg/L javelle water (sodium hypochlorite) or 15 mg/L bleaching powder(numerated by chlorine). The oxidation by using javelle water was rather stable when samples were varied in pH value, hardness, initial concentration of As(III) and As(III)/As(V) ratio. The effective oxidation could be reached with 1.25 mg/L javelle water when the initial concentration of As(III) was < or = 0.8 mg/L. Moreover, the field study also confirmed the oxidation effect of javelle water. It is suggested that javelle water is an effective, economic and technologic feasible oxidationagent for removing arsenite from dispersed drinking water.

Calmodulin binding properties of peptide analogues and fragments of the calmodulin-binding domain of simian immunodeficiency virus transmembrane glycoprotein 41

The calcium-regulatory protein calmodulin (CaM) can bind with high affinity to a region in the cytoplasmic C-terminal tail of glycoprotein 41 of simian immunodeficiency virus (SIV). The amino acid sequence of this region is (1)DLWETLRRGGRW(13)ILAIPRRIRQGLELT(28)L. In this work, we have used near- and far-uv CD, and fluorescence spectroscopy, to study the orientation of this peptide with respect to CaM. We have also studied biosynthetically carbon-13 methyl-Met calmodulin by (1)H, (13)C heteronuclear multiple quantum coherence NMR spectroscopy. Two Trp-substituted peptides, SIV-W3F and SIV-W12F, were utilized in addition to the intact SIV peptide. Two half-peptides, SIV-N (residues 1-13) and SIV-C (residues 13-28) were also synthesized and studied. The spectroscopic results obtained with the SIV-W3F and SIV-W12F peptides were generally consistent with those obtained for the native SIV peptide. Like the native peptide, these two analogues bind with an alpha-helical structure as shown by CD spectroscopy. Fluorescence intermolecular quenching studies suggested binding of Trp3 to the C-lobe of CaM. Our NMR results show that SIV-N can bind to both lobes of calcium-CaM, and that it strongly favors binding to the C-terminal hydrophobic region of CaM. The SIV-C peptide binds with relatively low affinity to both halves of the protein. These data reveal that the intact SIV peptide binds with its N-terminal region to the carboxy-terminal region of CaM, and this interaction initiates the binding of the peptide. This orientation is similar to that of most other CaM-binding domains.

[The experience of surgical resection in 1964 cases of primary bronchogenic carcinoma]

BACKGROUND

To summarize the experience of surgical resection of primary bronchogenic carcinoma (PBC) .

METHODS

We reviewed the clinicopathologic data of 1 964 cases of PBC. There were 1 140 central type and 824 peripheral type.

RESULTS

Among them, 1 626 cases ( 82. 8%, 1 626/ 1 964) were given successive resection, in which 160 cases were total pneumonectomy, 1 386 cases were lobectomy, 70 cases were sleeve lobectomy, and 10 cases were wedge resection. Two hundred and ninety2four cases had various postoperative complications and 20 cases died. The operative mortality was 1. 0%( 20/ 1 964) . Managements of problems encountered in operation were discussed in this paper.

CONCLUSIONS

Surgical resection is a better apporach in the treatment of PBC. Left upper lung cancer invading and surrounding the pulmonary artery trunk requires blocking the pulmonary artery root first, then separating the invaded blood vessels and resecting the tumor and upper pulmonary lobe, lastly dealing with the remained cancer tissues. For patients with intermediate and advanced lung cancer, if the root of pulmonary artery and vein almost attaches to the tumor, intrapericardial blood vessels ligation should be performed. When the right upper lung cancer invades and surrounds the superior vena cava and the upper pulmonary artery trunk, we should cut and ligate the azygos vein first and draw the superior vena cava gently towards front outside and dissect carefully. If the tumor, hilar, mediastinal and associated lymph nodesmix together to formthe frozen hilar, we should deal with the main bronchus first, then the pulmonary artery and vein.

[Thiol reagent thimerosal-induced Ca2+ mobilization in isolated guinea pig cochlear outer hair cells]

OBJECTIVE

To understand mechanism of cochlear outer hair cells (OHCs) intracellular Ca2+ mobilization further.

METHODS

Intracellular calcium of isolated guinea pig was investigated using thimerosal, a--SH group oxidizing agent, and fura-2 fluorescence ratio imaging microscopy.

RESULTS

In the presence of thimerosal, intracellular Ca2+ concentrations ([Ca2+]i) of OHCs were elevated in a dose-dependent manner. Even in Ca(2+)-free medium, Ca2+ response was still induced. The effects of thimerosal on [Ca2+]i were completely blocked and reversed by (DTT). Neither 1-100 mumol/L ryanodine nor 5-20 mmol/L caffeine altered the effects of thimerosal. Pretreatment with pertussis toxin (PTX) for 30 min did not affect the thimerosal-induced increase in [Ca2+]i The increase in [Ca2+]i when Ca2+ was added during thimerosal application in Ca(2+)-free medium was almost completely blocked by 500 mol/L LaCl3, while nifedipine did not inhibit further increase in [Ca2+]i caused by thimerosal.

CONCLUSION

Oxidation of the -SH group of the OHC membrane can induce a Ca2+ release from intracellular Ca2+ stores, which are ryanodine- and caffeine-insensitive, and Ca2+ influx through non-specific Ca2+ channels, but not the nifedipine-sensitive Ca2+ Channels. The possible oxidation of--SH group gated Ca2+ channels in OHCs are worthy of further study.

Mapping the interface between calmodulin and MARCKS-related protein by fluorescence spectroscopy

MARCKS-related protein (MRP) is a myristoylated protein kinase C substrate that binds calmodulin (CaM) with nanomolar affinity. To obtain structural information on this protein, we have engineered 10 tryptophan residues between positions 89 and 104 in the effector domain, a 24-residue-long amphipathic segment that mediates binding of MRP to CaM. We show that the effector domain is in a polar environment in free MRP, suggesting exposure to water, in agreement with a rod-shaped structure of the protein. The effector domain participates in the binding of MRP to CaM, as judged by the dramatic changes observed in the fluorescent properties of the mutants on complex formation. Intermolecular quenching of the fluorescence emission of the tryptophan residues in MRP by selenomethionine residues engineered in CaM reveals that the N-terminal side of the effector domain contacts the C-terminal domain of CaM, whereas the C-terminal side of the effector domain contacts the N-terminal domain of CaM. Finally, a comparison of the fluorescent properties of the myristoylated and unmyristoylated forms of a construct in which a tryptophan residue was introduced at position 4 close to the myristoylated N terminus of MRP suggests that the lipid moiety is also involved in the interaction of MRP with CaM.

[Study on the removal of arsenic from drinking water by coagulants]

The coagulation method for removing arsenic in drinking water from dispersed water supply was tested. The results showed that the remained arsenic [As(V)] in decanted water could be lower than 0.05 mg/L by directly putting 50 mg/L ferric sulfate into water samples without adjusting pH value (pH 7.82) and settling for 12 hours in room temperature while the original As(V) concentration was 1.0 mg/L. The same removal efficacy could be achieved by putting 30 mg/L ferric sulfate or 40 mg/L aluminum sulfate and filtering after 30-40 min settlement. The removal rates were raised with the increased concentration of coagulants in water. The remained As(V) in filtered water could meet the valid health standard of drinking water (< 0.05 mg/L) when the original concentrations of As(V) were 1.0 mg/L and 0.5 mg/L by using 30 mg/L ferric sulfate and aluminum sulfate respectively. Furthermore, ferric sulfate was more efficient than aluminum sulfate at varied of pH value, water temperature, turbidity and hardness of water, etc. Generally, arsenic in coagulated sludge would not release into water again.

Lentivirus-derived antimicrobial peptides: increased potency by sequence engineering and dimerization

We have previously described a family of cationic amphipathic peptides derived from lentivirus envelope proteins that have properties similar to those of naturally occurring antimicrobial peptides. Here, we explored the effects of amino acid truncations and substitutions on the antimicrobial potency and selectivity of the prototype peptide, LLP1. Removal of seven residues from the C-terminus of LLP1 had little effect on potency, but abrogated haemolytic activity. Replacement of the two glutamic acid residues of LLP1 with arginine resulted in a peptide with greater bactericidal activity. We discovered that the cysteine-containing peptides spontaneously formed disulphide-linked dimers, which were 16-fold more bactericidal to Staphylococcus aureus. Monomeric and dimeric LLP1 possessed similar alpha helical contents, indicating that disulphide formation did not alter the peptide's secondary structure. The dimerization strategy was applied to magainin 2, enhancing its bactericidal activity eight-fold. By optimizing all three properties of LLP1, a highly potent and selective peptide, named TL-1, was produced. This peptide is significantly more potent than LLP1 against gram-positive bacteria while maintaining high activity against gram-negative organisms and low activity against eukaryotic cells. In addition to new antimicrobial peptides, these studies contribute useful information on which further peptide engineering efforts can be based.

Surface exposure of the methionine side chains of calmodulin in solution. A nitroxide spin label and two-dimensional NMR study

Binding of calcium to calmodulin (CaM) causes a conformational change in this ubiquitous calcium regulatory protein that allows the activation of many target proteins. Met residues make up a large portion of its hydrophobic target binding surfaces. In this work, we have studied the surface exposure of the Met residues in the apo- and calcium-bound states of CaM in solution. Complexes of calcium-CaM with synthetic peptides derived from the CaM-binding domains of myosin light chain kinase, constitutive nitric-oxide synthase, and CaM-dependent protein kinase I were also studied. The surface exposure was measured by NMR by studying the effects of the soluble nitroxide spin label, 4-hydroxyl-2,2,6, 6-tetramethylpiperidinyl-1-oxy, on the line widths and relaxation rates of the Met methyl resonances in samples of biosynthetically 13C-methyl-Met-labeled CaM. The Met residues move from an almost completely buried state in apo-CaM to an essentially fully exposed state in Ca2+4-CaM. Binding of two Ca2+ to the C-terminal lobe of CaM causes full exposure of the C-terminal Met residues and a partial exposure of the N-terminal Met side chains. Binding of the three target peptides blocks the access of the nitroxide surface probe to nearly all Met residues, although the mode of binding is distinct for the three peptides studied. These data show that calcium binding to CaM controls the surface exposure of the Met residues, thereby providing the switch for target protein binding.

Calcium-dependent and -independent interactions of the calmodulin-binding domain of cyclic nucleotide phosphodiesterase with calmodulin

The ubiquitous Ca2+-binding regulatory protein calmodulin (CaM) binds and activates a wide range of regulatory enzymes. The binding is usually dependent on the binding of Ca2+ to CaM; however, some target proteins interact with CaM in a calcium-independent manner. In this work, we have studied the interactions between CaM and a 20-residue synthetic peptide encompassing the major calmodulin-binding domain of cyclic nucleotide phosphodiesterase (PDE1A2). The binding was studied in the absence and presence of Ca2+ by far-UV and near-UV circular dichroism, fluorescence, and infrared spectroscopy. In addition, two-dimensional heteronuclear NMR studies with 13C-methyl-Met-CaM and uniformly 15N-labeled CaM were performed. Competition assays with smooth muscle myosin light chain kinase revealed a Kd of 224 nM for peptide binding to Ca2+-CaM, while binding of the peptide to apo-CaM is weaker. The peptide binds with an alpha-helical structure to both lobes of Ca2+-saturated CaM, and the single Trp residue is firmly anchored into the C-terminal lobe of CaM. In contrast, the Trp residue plays a minor role in the binding to the apo-protein. Moreover, when bound to apo-CaM, the PDE peptide is only partially helical, and it interacts solely with the C-terminal lobe of CaM. These results show that the Ca2+-induced activation of PDE involves a significant change in the structure and positioning of the CaM-bound PDE peptide domain.

Molecular mechanisms of calmodulin's functional versatility

Calmodulin (CaM) is a primary Ca2+-binding protein found in all eukaryotic cells. It couples the intracellular Ca2+ signal to many essential cellular events by binding and regulating the activities of more than 40 different proteins and enzymes in a Ca2+-dependent manner. CaM contains two structurally similar domains connected by a flexible central linker. Each domain of the protein binds two Ca2+ ions with positive cooperativity. The binding of Ca2+ transforms the protein into its active form through a reorientation of the existing helices of the protein. The two helices in each helix-loop-helix Ca2+-binding motif are almost antiparallel in Ca2+-free CaM. The binding of Ca2+ induces concerted helical pair movements and changes the two helices in each Ca2+ binding motif to a nearly perpendicular orientation. These concerted helix pair movements are accompanied by dramatic changes on the molecular surface of the protein. Rather than exhibiting a flat, hydrophilic molecular surface as seen in Ca2+-free CaM, the Ca2+-saturated form of the protein contains a Met-rich, cavity-containing hydrophobic surface in each domain. These hydrophobic surfaces are largely responsible for the binding of CaM to its targets. The unique flexibility and high polarizability of the Met residues located at the entrance of each hydrophobic pocket together with other hydrophobic amino acid residues create adjustable, sticky interaction surface areas that can accommodate CaM's targets, which have various sizes and shapes. Therefore, CaM is able to bind to a large array of targets without obvious sequence homology. Upon binding to its target peptides, the unwinding of the central linker allows the two domains of the protein to engulf the hydrophobic face of target peptides of differing lengths. The binding of Ca2+ reduces the backbone flexibility of CaM. Formation of complexes with its target peptides further decreases the backbone motion of CaM.

Substitution of the methionine residues of calmodulin with the unnatural amino acid analogs ethionine and norleucine: biochemical and spectroscopic studies

Calmodulin (CaM) is a 148-residue regulatory calcium-binding protein that activates a wide range of target proteins and enzymes. Calcium-saturated CaM has a bilobal structure, and each domain has an exposed hydrophobic surface region where target proteins are bound. These two "active sites" of calmodulin are remarkably rich in Met residues. Here we have biosynthetically substituted (up to 90% incorporation) the unnatural amino acids ethionine (Eth) and norleucine (Nle) for the nine Met residues of CaM. The substituted proteins bind in a calcium-dependent manner to hydrophobic matrices and a synthetic peptide, encompassing the CaM-binding domain of myosin light-chain kinase (MLCK). Infrared and circular dichroism spectroscopy show that there are essentially no changes in the secondary structure of these proteins compared to wild-type CaM (WT-CaM). One- and two-dimensional NMR studies of the Eth-CaM and Nle-CaM proteins reveal that, while the core of the proteins is relatively unaffected by the substitutions, the two hydrophobic interaction surfaces adjust to accommodate the Eth and Nle residues. Enzyme activation studies with MLCK show that Eth-CaM and Nle-CaM activate the enzyme to 90% of its maximal activity, with little changes in dissociation constant. For calcineurin only 50% activation was obtained, and the K(D) for Nle-CaM also increased 3.5-fold compared with WT-CaM. These data show that the "active site" Met residues of CaM play a distinct role in the activation of different target enzymes, in agreement with site-directed mutagenesis studies of the Met residues of CaM.

Calcium-calmodulin-induced dimerization of the carboxyl-terminal domain from petunia glutamate decarboxylase. A novel calmodulin-peptide interaction motif

The acidic, bilobed protein calmodulin (CaM; molecular mass of 16.7 kDa) can activate some 40 distinct proteins in a calcium-dependent manner. The majority of the CaM-binding domain regions of the target proteins are basic and hydrophobic in nature, are devoid of multiple negatively charged residues, and have a propensity to form an alpha-helix. The CaM-binding domain in the C-terminal region of petunia glutamate decarboxylase (PGD) is atypical because it contains five negatively charged residues. Therefore, we chose to study the binding of calcium-CaM to a 26-residue synthetic peptide encompassing the C-terminal region of PGD. Gel band shift assays, fluorescence spectroscopy, and NMR titration studies showed that a single unique complex of calcium-CaM with two PGD peptides is formed. The formation of a 1:2 protein-peptide complex is unusual; normally, calcium-CaM forms 1:1 complexes with the majority of its target proteins. Circular dichroism spectroscopy showed that the bound PGD peptides have an alpha-helical structure. NMR studies of biosynthetically [methyl-13C]methionine-labeled CaM revealed that all the Met side chains in CaM are involved in the binding of the PGD peptides. Analysis of fluorescence spectra showed that the single Trp residue of the two peptides becomes bound to the N- and C-terminal lobes of CaM. These results predict that binding of calcium-CaM to PGD will give rise to dimerization of the protein, which may be necessary for activation. Possible models for the structure of the protein-peptide complex, such as a dimeric peptide structure, are discussed.

Characterization of the Ca2+ -dependent and -independent interactions between calmodulin and its binding domain of inducible nitric oxide synthase

Most interactions of calmodulin (CaM) with its target proteins are Ca2+-dependent, but a few Ca2+-independent CaM-target protein interactions have been identified. One example is the inducible isoform of nitric oxide synthase (iNOS) expressed in macrophages. We describe here the characterization of the Ca2+-independent interaction between CaM and a synthetic peptide corresponding to the CaM-binding domain of murine macrophage iNOS using circular dichroism (CD) spectroscopy. The CD spectrum of free iNOS peptide indicated a beta-sheet conformation. The interaction of iNOS peptide with apo-CaM in the absence of Ca2+ resulted in the peptide acquiring a type II beta-turn structure. This is in contrast to the situation in the presence of Ca2+ in which case the peptide acquired an alpha-helical conformation upon interaction with CaM, i.e. similar to the Ca2+-dependent interactions of CaM with numerous targets such as myosin light chain kinase (MLCK). Consistent with this similar structural change, iNOS peptide inhibited the Ca2+-CaM-dependent activation of smooth muscle MLCK by competing with MLCK for binding to Ca2+-CaM. The Kd of Ca2+-CaM for iNOS peptide was calculated from competition assays to be 0.3 nM. These results indicate that the structure of the CaM-binding domain of iNOS is quite different when bound to apo-CaM than Ca2+-CaM.

[The use of predforte in the transnasal endoscopic sinus surgery]

For finding a way to advance the healing of the operative cavity after transnasal endoscopic sinus surgery (TESS). Predforte (mixt 10% prednisolone acetate) was administered transnasally to the operative cavity of 75 cases who accepted TESS. 13 cases (17.5%) were brought about a striking effect, the good results were achieved on the 56 cases. The total effective rate was 92.0%. The results suggest that the mixture could be distributed better and effected longer in comparison with the solution of predinisolone acetate.

Tryptophan fluorescence quenching by methionine and selenomethionine residues of calmodulin: orientation of peptide and protein binding

The two interaction surfaces of the dumbbell-shaped calcium-regulatory protein calmodulin (CaM) are rich in the amino acid Met. In this work we have used fluorescence spectroscopy to study the role of these Met residues in binding the single Trp residue that is found in many CaM-binding domain peptides. This approach is facilitated by the absence of Trp residues in CaM. In addition to the wild-type protein, we studied CaM containing the unnatural amino acid selenomethionine (SeMet), which was biosynthetically substituted for its nine Met residues. Furthermore, a CaM mutant protein in which all four Met residues in the C-terminal domain were mutated to Leu, and the N-terminal domain contained either Met or the unnatural SeMet, was studied. The Trp fluorescence quantum yield of many Trp-containing CaM-binding peptides increases upon binding to calcium-CaM. Moreover, the emission wavelength of the Trp fluorescence is blue-shifted from 353 to 325-333 nm. These parameters indicate movement of Trp from a solvent exposed to a hydrophobic environment. The fluorescence results obtained with these four CaM variants showed that Se is very effective at quenching Trp fluorescence in the calmodulin-bound peptides from myosin light chain kinase (MLCK) and CaM kinase I, while S is somewhat effective (Se > S > C). The quenching effect is markedly distance dependent, as it only influences the Trp residue of the bound peptide (<=7 A) but has little effect on the two Tyr residues in the C-terminal domain of CaM (>=10 A). Since the Trp fluorescence quenching is very dramatic, the protein containing Leu's in the C-terminal domain and SeMet's in the N-terminal domain allowed us to directly determine the orientation of the MLCK and CaM kinase I peptides bound to CaM; in both cases the Trp residue binds to the C-terminal domain of CaM. Our data indicate that SeMet quenching of Trp fluorescence could become a simple and useful tool for studies of protein folding, and protein-protein and protein-peptide interactions.