Flow rate dependent kinetics of urease immobilized onto diverse matrices

Gas holdup and liquid circulation velocity meassurements were made for a range of liquid viscosities in a 22 l external loop airlift column and 250 l pilot-scale concentric cylinder airlift bioreactor. The results showed that for a fixed superficial gas velocity, liquid circulation velocity decreased monotonically with increasing liquid viscosity. The gas holdup for a fixed gas flow rate showed an initial increase with liquid viscosity followed by a decrease when liquid viscosity increased beyond a critical value. These observations could not be described satisfactorily using the available models of gas holdup and liquid circulation.List of Symbols U _sg m/s Superficial gas velocity - U _sl m/s Superficial liquid velocity in the riser Greek Letters Pas Liquid viscosity - _g Gas holdup in the riser     

Study of the liquid circulation velocity in external-loop airlift bioreactors

Liquid circulation velocity was studied in externalloop air-lift bioreactors of laboratory and pilot scale, respectively for different gas input rates, downcomer-to-riser cross-sectional area ratio, A _D/A_R and liquid phase apparent viscosities.It was found that, up to a gas superficial velocity in the riser v _SGR 0.04 m/s the dependency of v _SLR on v _SGR is in the following form: v _SLR = a v _SGR ^b , with the exponent b being 0.40. Over this value of v _SGR, only a small increase in liquid superficial velocity, v _SLR is produced by an increase in v _SGR. A _D/A_R ratio affects the liquid superficial velocity due to the resistance in flow and overall friction.For non-Newtonian viscous liquids, the circulation liquid velocity in the riser section of the pilot external-loop airlift bioreactor is shown to be dependent mainly on the downcomer-to-riser cross-sectional area ratio, A _D/A_R, the effective (apparent) liquid viscosity, _eff and the superficial gas velocity, v _SGR.The equation proposed by Popovic and Robinson [11] was fitted well, with an error of ± 20%.List of Symbols A _D m² downcomer cross-sectional area - A _Rm² riser cross-sectional area - a = coefficient in Eq. (7) - b = exponent in Eq. (7) - c _s m^–1 Coefficient in Eq. (3) - D _D m downcomer diameter - D _R m riser diameter - g m²/s gravitational acceleration - H _D m dispersion height - H _L m ungassed liquid height - K Pa s ⁿ consistency index - K _B = friction factor at the bioreactor bottom - K _F = friction factor - K _T = friction factor at the bioreactor top - V _L m³ liquid volume in the bioreactor - V _D m³ liquid volume in downcomer - V _R m³ liquid volume in riser - v _LDm/s downcomer linear liquid velocity - v _LR m/s riser linear liquid velocity - v _SGR m/s riser superficial liquid velocity - v _SLR m/s riser superficial liquid velocity - s^–1 shear rate - _GD = downcomer gas holdup - _GR = riser gas holdup - _eff Pa s effective (apparent) viscosity - Pa shear stress The authors wish to thank Mrs. Rodica Roman for the help in experimental data collection and to Dr. Stefanluca for the financial support.     

Liquid-phase axial mixing in a bubble column bioreactor containing yeast suspensions

Summary Liquid-phase axial mixing coefficients were evaluated in a 0.15 m x 2.0 m batch bubble column containing water and yeast-in-water suspensions of different concentrations. Air superficial velocities ranged from 0 to 0.06 m/s. Axial mixing coefficients were calculated from the residence time distribution to an NaCl tracer pulse using the Ohki and Inuoe model. No specific variations in the calculated coefficients were observed to result from the presence of yeast cells. There was fair agreement between the data thus obtained and the only available data on mixing in non-Newtonian CMC solution.Nomenclature C _E equilibrium tracer concentration g/l - C tracer concentration at time t g/l - d_h sparger hole diameter m - D _t tube diameter m - D _z axial mixing coefficient m²/s - g acceleration of gravity m/s² - H _B bubbling layer heigh m - L longitudinal dustance between tracer injection and detection points m - n 1,2,6 Eq. (3) - t time s - U_g gas superficial velocity m/s - U_t liquid superficial velocity m/s - V _r bubble relative velocity = m/s - V _t Linear relative velocity m/s - z axial distance m Greek _c wet cell volume farction - _g gas holdup - _l liquid holdup - _l viscosity of the liquid phase Pa/s - _l density of liquid or continuous phase g/ml     

Gas holdup and mass transfer characteristics of carboxymethyl cellulose solutions in a bubble column with a radial gas sparger

The gas phase holdup and mass transfer characteristics of carboxymethyl cellulose (CMC) solutions in a bubble column having a radial gas sparger have been determined and a new flow regime map has been proposed. The gas holdup increases with gas velocity in the bubbly flow regime, decreases in the churn-turbulent flow regime, and increases again in the slug flow regime. The volumetric mass transfer coefficient (k _La) significantly decreases with increasing liquid viscosity. The gas holdup and k _La values in the present bubble column of CMC solutions are found to be much higher than those in bubble columns or external-loop airlift columns with a plate-type sparger. The obtained gas phase holdup ( _g) and k _La data have been correlated with pertinent dimensionless groups in both the bubbly and the churn-turbulent flow regimes.List of Symbols a m^–1 specific gas-liquid interfacial area per total volume - A _d m² cross-sectional area of downcomer - A _r m² cross-sectional area of riser - d _b m individual bubble diameter - d _vs m Sauter mean bubble diameter - D _c m column diameter - D _L m²/s oxygen diffusivity in the liquid - Fr Froude number, U _g/(g D_c)^1/2 - g m/s² gravitational acceleration - G _a Galileo number, gD _c ^{3 2}/² _app - H _a m aerated liquid height - H _c m unaerated liquid height - K Pa · sⁿ fluid consistency index - k _L a s^–1 volumetric mass transfer coefficient - n flow behavior index - N _i number of bubbles having diameter d _bi - Sc Schmidt number, _app/( D _L) - Sh Sherwood number, k _L a D _c ² /D_L - U _sg m/s superficial gas velocity - U _gr m/s superficial riser gas velocity - V _a m³ aerated liquid volume - V _c m³ unaerated liquid volume - N/m surface tension of the liquid phase - _g gas holdup - _app Pa · s effective viscosity of non-Newtonian liquid - kg/m³ liquid density - ý s^–1 shear rate - Pa shear stress     

Purification and characterization of bovine brain calmodulin-dependent protein kinase II. The significance of autophosphorylation in the regulation of 63 kDa calmodulin-dependent cyclic nucleotide phosphodiesterase isozyme

Bovine brain contains two calmodulin-dependent phosphodiesterase kinases which are separated on Sephacryl S-300 column. One of these kinases has been purified to homogeneity and shown to belong to the calmodulin-dependent protein kinase II family. Phosphorylation of the 63 kDa phosphodiesterase by this purified protein kinase results in the incorporation of 1.0 mol phosphate per mol subunit and an accompanying increase in Ca²⁺ concentrations required for the phosphodiesterase activation by calmodulin. The protein kinase undergoes autophosphorylation to incorporate 1.0 mol phosphate per mol of subunit of the enzyme and the autophosphorylated enzyme is active, independent of the presence of Ca²⁺. The autophosphorylation reaction as well as the protein kinase reaction are rendered Ca²⁺ independent in less than 15 seconds when approximately one mol phosphate per mol protein kinase is incorporated. The result suggests that activation of phosphodiesterase phosphorylation reaction may occur prior to the activation of phosphodiesterase and phosphatase during a cell Ca²⁺ flux via the protein kinase autophosphorylation mechanism.Abbreviations SDS sodium dodecyl sulfate - EGTA ethylene glycol bis (-aminoethyl ether) - N,N,N,N tetra acetic acid - EDTA ethylenediamine-tetraacetic acid - cAMP cyclic adenosine 35 monophosphate This work is supported by grants from the Medical Research Council of Canada (JHW), the Heart and Stroke Foundation of Alberta (JHW and RKS) and the Heart and Stroke Foundation of Saskatchewan (RKS)     

Foam behavior of biological media

Summary The surface tension and foaminess of (a) unlimited, (b) substrate limited, and (c) oxygen transfer limited growth media of Hansenula polymorpha were measured using methanol, ethanol or glucose as a substrate.The time dependence of can be described by the Avrami-Überreiter relationship: log (2.3 log V)=n log t+log b, where V = (_O – _eq/(_t – _eq, and _O, _t and _eq are at t_M=0, t_M=t and t_M (equilibrium value).The constants n and b are functions of the fermentation time t_F as long as the growth is unlimited but they are constant in the state of limited growth. With glucose substrate, the foaminess can be presented as a definite function of the time, t_DG, which is necessary to attain _eq. With alcohol as a substrate no definite (t_DG) function was found.Symbols b constant in Eq. (1) - n constant in Eq. (1) - S substrate concentration - T temperature - t_M time h (measured from the beginning of the determination of the surface tension ) - t_F cultivation time h (measured from the time of inoculation) - t_DG time (min) necessary to attain the equilibrium surface tension ) - X dry biomass concentration (gl^–1) - V (_O – _eq)/(_t – _eq) - V_S equilibrium volume of the foam (cm³) - V_G volumetric gas flow rate during the estimation of (cm³ s^–1) - vvm volumetric gas flow rate with regard to the volume of the medium (min^–1) - w_SG superficial gas velocity (cm s^–1) - _m maximum specific growth rate (h^–1) - V_S/V_G foaminess (s) - surface tension, mMm^–1 (milli Newton m^–1) - _O at t_M=0 - _eq equilibrium surface tension ( at t_M) - _t at t_M=t - HP probes from Hansenula polymorpha cultivation - NLG non limited growth - OTLG oxygen transfer limited growth - SLG substrate limited growth     

Residence time distribution of liquid phase in an external-loop airlift bioreactor

The residence time distribution analysis was used to investigated the flow behaviour in an external-loop airlift bioreactor regarded as a single unit and discriminating its different sections. The experimental results were fitted according to plug flow with superimposed axial dispersion and tank-in-series models, which have proved that it is reasonable to assume plug flow with axial dispersion in the overall reactor, in riser and downcomer sections, as well, while the gas separator should be considered as a perfectly mixed zone. Also, the whole reactor could be replaced with 105-30 zones with perfect mixing in series, while its separate zones, that is the riser with 104-27, the downcomer with 115-35 and the gas separator with 25-5 perfectly mixed zones in series, respectively, depending on gas superficial velocity, A_D/A_R ratio and the liquid feed rate.List of Symbols A _D cross sectional area of downcomer (m²) - A _R cross sectional area of riser (m²) - A ₁ A ₂ length of connecting pipes (m) - Bo Bodenstein number (Bo=vL·L/D _ax (-) - C concentration (kg m^–3) - C residence time distribution function - C ₀ coefficientEquation (12) - C _r dimensionless concentration - D _D diameter of downcomer (m) - D _R diameter of riser column (m) - D _ax axial dispersion coefficient (m²s^–1) - H _d height of gas-liquid dispersion (m) - H _L height of clear liquid (m) - i number of complete circulations - L length of path (m) - m order of moments - N _eq number of perfectly mixed zones in series - n _c circulating number - Q _c recirculating liquid flow rate (m³ s^–1) - q _F liquid feed flow rate (m³s^–1) - Q _G gas flow rate (m³s^–1) - Q _T total liquid flow rate (m³s^–1) - r recycle factor - s exponent inEquation (12) regarded as logarithmic decrement of the oscillating part of RTD curve - t time (s) - t _C circulation time (s) - t _s mean residence time (s) - t ₉₉ time necessary to remove 99% of the tracer concentration (s) - V _A volume of connecting pipes (m³) - V _D volume of downcomer (m³) - V _L liquid volume in reactor (m³) - V _R volume of riser (m³) - V _LD linear liquid velocity in downcomer (m s^–1) - V _LR linear liquid velocity in riser (m s^–1) - V _SLD superficial liquid velocity in downcomer (m s^–1) - V _SLR superficial liquid velocity in riser (m s^–1) - x independent variable inEquation (1) - ¯x mean value of x - z axial coordinate - _GR gas holdup in riser - _m(x) central moment of m order - ² variance - dimensionless time     

IP3-and cAMP-induced responses in isolated olfactory receptor neurons from the channel catfish

Summary Olfactory receptor neurons enzymatically dissociated from channel catfish olfactory epithelium were depolarized transiently following dialysis of IP₃ or cAMP (added to the patch pipette) into the cytoplasm. Voltage and current responses to IP₃ were blocked by ruthenium red, a blocker of an IP₃-gated Ca²⁺-release channel in sarcoplasmic reticulum. In contrast, the responses to cAMP were not blocked by extracellularly applied ruthenium red, nor by l-cis-diltiazem or amiloride and two of its derivatives. The current elicited by cytoplasmic IP₃ in neurons under voltage clamp displayed a voltage dependence different from that of the cAMP response which showed marked outward rectification. A sustained depolarization was caused by increased cytoplasmic IP₃ or cAMP when the buffering capacity for Ca²⁺ of the pipette solution was increased, when extracellular Ca²⁺ was removed or after addition of 20–200 nm charibdotoxin to the bathing solution, indicating that the repolarization was caused by an increase in [Ca _i ] that opened Ca²⁺-activated K⁺ channels. The results suggest that different conductances modulated by either IP₃ or cAMP are involved in mediating olfactory transduction in catfish olfactory receptor neurons and that Ca²⁺-activated K⁺ channels contribute to the termination of the IP₃ and cAMP responses.Abbreviations ATP adenosine 5-triphosphate - BAPTA (bis-(o-aminophenoxy)-ethane-N-N-N-N)-tetraacetic acid - cAMP adenosine cyclic 3,5-monophosphate - cGMP guanosine cyclic 3,5-monophosphate - CTX charybdotoxin - DCB 3,4-dichlorobenzamil - EDTA ethylenediaminetetraacetic acid - EGTA ethylenglycol-bis-(b-aminoethyl)-N-N-N-N-tetraacetic acid - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - IP₃ inositol-1,4,5-triphosphate - NMDG N-methyl-d-glucamine We would like to thank the Tanabe Seiyaku Co., Ltd., for their gift of l-cis-diltiazem. This work was supported by National Institutes of Health grants DC00566 and BRSG S07RR05825.     

Characterization of the reciprocal binding sites on human α-thrombin and factor XIII A-chain

Solution- and solid-phase techniques were used to probe Factor XIII A-chain-a-thrombin interactions. -Thrombin activated Factor XIII more efficiently (Km = 0.83 ± 0.08 × 10^-7 M; V/K = 14.90 ± 3.20 × 10^-3 min^-1) than -thrombin (Km = 6.14 ± 1.26 × 10^-7 M; V/K = 3.30 ± 1.00 × 10^-3 min^-1) or -thrombin (Km = 6.25 ± 1.15 × 10^-7 M; V/K = 3.00 ± 0.80 × 10^-3 min^-1). Immobilized FPR--thrombin bound plasma Factor XIII (Kd = 0.17 ± 0.04 × 10^-7 M) > Factor XIIIa (Kd = 0.69 ± 0.18 × 10^-7 M) > liver transglutaminase (Kd = 4.73 ± 1.01 × 10^-7 M) > Factor XIII A-chain (Kd = 49.00 ± 9.40 × 10^-7 M). FPR--thrombin and -thrombin also bound immobilized Factor XIII A-chain with affinities inversely related to protease activity: maximal binding at 1.36 × 10^-7 M and 13.6 × 10^-7 M, respectively. Plasma Factor XIII, transglutaminase, and dithiothreitol competitively inhibited Factor XIII A-chain binding to FPR--thrombin: IC₅₀ = 1.0 × 10^-7 M, 3.0 × 10^-6 M and 1.52 × 10^-4 M, respectively. Transglutaminase also inhibited Factor XIII binding to ×-thrombin (IC₅₀ = 2.0 × 10^-6 M). Thrombin-binding site was localized to G^-38-M^-731 fragment of Factor XIII A-chain, probably within homologous regions (N^-72-A^-493) of transglutaminase. R^-320-E^-579 of -thrombin was Factor XIII A-chain binding site. Intra-B-chain disulfides in -thrombin were essential for binding but not catalytic H^-363 or residues R^-382-N^-394 and R^-443-G^-475. These studies propose a structural basis for Factor XIII activation, provide a regulatory mechanism for Factor XIIIa generation, and could eventually help in the development of new structure-based inhibitors of thrombin and Factor XIIIa.     

Circular Dichroism Studies of the Interaction of Tat Analogues Substituted in the Arg52 Position with TAR RNA HIV-1

The Tat wild-type fragment of sequence Arg⁴⁹-Lys-Lys-Arg⁵²-Arg-Gln-Arg-Arg-Arg⁵⁷-NH₂ (labelled as Tat1) and three analogues of this fragment with the substitution Arg⁵² D-Arg⁵² (labelled as Tat2) or L-citrulline (Cit) (labelled as Tat3) or L-ornithine (Orn) (labelled as Tat4) were synthesized to study Tat-TAR RNA HIV-1 (27-nucleotide fragment of sequence 5-AGAUCUGAGCCUGGAGCUCUCU-3) interactions by circular dichroism. -helical structure was the most readily adopted by the Tat3 analogue with Arg⁵² Cit substitution. All the peptides investigated caused conformational changes in the TAR structure. The most dramatic changes were observed for the Tat2-TAR complex.     

Conformational energy of the 5-membered ring. Implication of geometric and energetic properties in the conformational characteristics

In a previous article (8) a geometrical study of the five-membered ring showed that: a) for the case of the 20 symmetrical C₂ and C_s conformations, the pseudorotation formulae for the torsion angles are a geometrical property of the ring; b) geometrical considerations alone are unable to define the puckering amplitude, the bond angle values, and the pathway between two symmetrical conformations. Here we examine how the energy equations enable us to define the deformation amplitude _m, establish the bond angles expressions and check the energy invariability along the pseudorotation circuit. The problem is next developed fully in the case where the bond and torsional energy only are considered: the literal expression¹ of _m is then given as a function of the bond angle which cancels out the bond angle energy. A numerical application is carried out on cyclopentane and the values of the parameters K^t, K¹ and used in the Conformational energy calculations are considered.Notations used 1 _i bond lengths 1 in the case of the regular ring - _i torsional angles - _i bond angles - 3/5 = 108 - 4/5 = 144 - , _{i i} – = complement to the 108 bond angle _i - _T - E Conformational energy of the 5-membered ring - E Conformational energy difference between planar and deformed ring - A _n Coefficients of the energy development in terms of - E _i ^l Bond energy relative to atom i (associated with angle _i) - K _i ^l Bond constant relative to atom i (associated with angle _i) - E _i ^l Torsional energy relative to the i ^th bond (associated with angle _i) - k _i ^l Torsional constant relative to the i ^th bond (associated with angle _i) - _i Angle _i value corresponding to zero bond energy E _i ^l (when the 5 atoms of the ring are identical, _i ) - r _ij Distance between atoms i and j - q _i Charge carried by atom i - e Constant of proportionality including the effective dielectric constant - A _ij, B_ij, d_ij Coefficients dependent on the nature of the atoms i and j and accounted for in the Van der Waals energy and hydrogen bond expressions - S (r _ij) Electrostatic contribution to the hydrogen bond energy - P Pseudorotation phase angle - _m Maximum torsional angle value characterising the deformation amplitudeM     

Oxygen mass transfer in a bubble column bioreactor containing lysed yeast suspensions

Summary Liquid-phase volumetric oxygen transfer coefficients were evaluated in a bubble column containing yeast suspensions, using the instationary oxygen absorption method and a polarographic oxygen electrode. The electrode time lag was found to be independent of both the system studied and the operating conditions. The volumetric oxygen mass transfer coefficients k _L a could be reasonably predicted by calculating k _L from the equation derived by Bhavaraju et al. or the empirical equation of Calderbank and Moo-Young and a from the experimental gas hold-up values.Nomenclature a Exponent in Eq.6 or specific gas-liquid interfacial area based on reactor volume m - b Exponent in Eq. 6 - C Constant in Eq 6 or oxygen concentration in the liquid phase g/ml - C ^* Equilibrium oxygen concentration g/ml - C ₀ Oxygen concentration in the liquid phase at t=0 g/ml - C _E Oxygen concentration as determined by the polarographic electrode g/ml - D _B Bubble equivalent diameter mm - D _l Oxygen diffusivity in the liquid phase m²/s - g Acceleration of gravity m/s² - K Consistency index Pasⁿ - K _L Liquid-phase mass transfer coefficient m/s - n Power law exponent - Pe _sw Peclet number based on bubble swarm velocity - S _C Schmidt number - Sh Sherwood number - i Time s - U _B Bubble rise velocity in infinite medium m/s - U _g Superficial air velocity based on column cross-sectional area m/s - U _sw Bubble swarm velocity defined by Eq.15 m/s - Y _MSW Mass transfer coeficient correction factor for mobile interfaces in pseudo-plastic fluids Eq. 7 - Y _MSW Mass transfer coefficient correction factor for immobile interface in pseudo-plastic fluids Eq. 8 Greek letters _l Density of liquid g/ml - _sus Density of unaerated suspension g/ml - _{wet cell} Density of yeast wet cells g/ml - _l Viscosity of the liquid Pas - _app Apparent viscosity of power law fluid Pas - _E Electrode time lag s - _l Time lag due to resistance of the gas-liquid interface s - _g Gas hold-up, volume fraction occupied by the gas phase - _l Liquid hold-up - _c Wet cell volume fraction     

Determination of the transmembrane proton gradient in the anaerobic bacterium Desulfovibrio desulfuricans by 31P nuclear magnetic resonance

The transmembrane proton gradient of the sulfate-reducing bacterium Desulfovibrio desulfuricans strain CSN has been determined by in vivo³¹P nuclear magnetic resonance (NMR) spectroscopy in the absence of dioxygen. At pH 7.0 in the medium (pH_ex) the intracellular pH (pH_in) was 7.5. By lowering pH_ex to 5.9 pH_in decreased to 7.1. At pH_ex greater than 7.7 the transmembrane proton gradient (pH) was zero. The uncouplers 3,3,4,5-tetrachlorosalicylanilide (TCS) and carbonylcyanide-m-chlorophenylhydrazone (CCCP), or the permeant anion thiocyanate caused complete dissipation of pH.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - TCS 3,3,4,5-tetrachlorosalicylanilide - MOPS 3-(N-morpholino)-propanesulfonic acid - P _i inorganic phosphate - pH _in (pH_ex) intracellular (extracellular) pH - pH transmembrane proton gradient (pH_in-pH_ex) - electrochemical membrane potential - chemical shift in parts per million - NMR nuclear magnetic resonance     

A sensitive and robust method for obtaining intermolecular NOEs between side chains in large protein complexes

A method for measuring intermolecular NOEs in protein complexes based on asymmetric sample deuteration is described. ¹³C/¹H-I,L,V-methyl, U-²H labeled protein is produced using the biosynthetic precursors [-¹³C]--ketobutyrate and [,-¹³C₂]--ketoisovalerate. The labeled protein is mixed with its unlabeled binding partner and a 3D ¹³C-HMQC-NOESY is recorded, yielding unambiguous intermolecular aromatic/methyl NOEs. A simple synthesis of the biosynthetic precursors via reaction of diethyl oxalate with alkyl Grignard compounds is reported. The method is demonstrated for a 35 kDa heterodimeric protein complex dissolved in a CHAPS micelle. This approach will facilitate the solution structure determination of protein/protein, protein/ligand or protein/nucleic acid complexes.These authors contributed equallyThese authors contributed equally     

Study of a cable contactor in ultra-violet disinfection

Summary This preliminary study investigates the possible use of a cable contactor for the sterilization of micro-organisms suspensions in water by ultra-violet radiation. The influence of some of the most important operating parameters has been analysed and a kinetic model of UV disinfection in the AMAZONE contactor is proposed. The technical feasibility of the process is seemingly demonstrated.Notations I UV light intensity (W/m²) - j Number of passages on the cables - k Kinetic parameter - n Kinetic parameter (m²/J) - N_O Initial number of m.o. (m.o./ml) - N_S Surviving m.o. at time t (m.o./ml) - Mean residence time=V/Q (s) - Q Liquid circulation flow rate (m³/s) - t Time (s) - T Mean residence time of the liquid on the cables (s) - V Holding tank volume (m³)     

Negative-ion fast atom bombardment and electrospray ionization tandem mass spectrometry for characterization of sulfated and sialyl Lewis-type glycosphingolipids

Structural characterization of sulfated and sialyl Lewis (Le)-type glycosphingolipids performed by fast atom bombardment (FAB) and electrospray ionization (ESI) mass spectrometry is described. Both FAB and ESI collision-induced dissociation tandem mass spectrometry (CID-MS/MS) of acidic glycosphingolipids allowed identification of the sulfated or sialyl sugar, and provided information on the saccharide chain sequence. The negative-ion tandem FABMS of sulfated Le-type glycosphingolipids having the non-reducing end trisaccharide ion as the precursor can be used to differentiate the Le^a- and Le^X-type oligosaccharides. The ESI CID-MS/MS of multiple-charged ions provided even more detailed structural information, and some of the useful daughter ions appeared with higherm/z values than the precusor because of a lower charge-state. These methodologies can be applied to the structural analyses of glycoconjugates with much larger molecular masses and higher polarity, such as the poly-sulfated and sialyl analogues.Abbreviations CID collision-induced dissociation - ESI electrospray ionization - FABMS fast atom bombardment mass spectrometry - Fuc fucose - Gal galactose - GlcNAc N-acetylglucosamine - Le Lewis - Le^a Lewis^a - Le^X Lewis^X - MS/MS mass spectrometry/mass spectrometry - NeuAc N-acetylneuraminic acid - 3-SO₄-Le^a 3-sulfated Le^a pentaosyl ceramide - 3-SO₄-Le^X 3-sulfated Le^X pentaosyl ceramide - 2,3-SO₄-Le^X 2,3-disulfated Le^X pentaosyl ceramide - 3-S-Le^a 3-sialyl Le^a pentaosyl ceramide - 3-S-Le^x 3-sialyl Le^X heptaosyl ceramide - 3-S-Le^X-Le^X 3-sialyl-Le^x-Le^x octaosyl ceramide.     

Bubble coalescence behaviour in biological media

Summary Volumetric mass transfer coefficients (k_La) were measured by a steady state method in a twin bubble column to characterize the coalescence behaviour of the medium. Employing Hansenula polymorpha cultivation broths, k_La values were compared with those measured in model media in the presence and absence of antifoam agents. The ratio of the volumetric mass transfer coefficient in the system investigated to that in water, , was employed to characterize the cultivation medium.Symbols a Specific gas/liquid interfacial area with regard to the liquid volume in reactor - d_e Dynamical equilibrium bubble diameter - d_H Perforated plate hole diameter - d_p Primary bubble diameter - d_S Sauter bubble diameter - F_v Liquid feed rate - H Bubbling layer height - k_L Gas/liquid mass transfer coefficient - k_La Volumetric mass transfer coefficient - m k_La/(k_La)_r coalescence index - m_corr Corrected coalescence index [Eq. (3)] - OTR Oxygen transfer rate - P_O Dissolved O₂-partial pressure in BS2 - P₁ Dissolved O₂-partial pressure in BS1 - P_O P_O/P_S relative oxygen saturation in BS2 - P₁ P₁/P_S relative oxygen saturation in BS1 - P_S Saturation dissolved oxygen partial pressure - R_c dn_B/dt coalescence rate - S Substrate concentration - t_F Time since the beginning of the cultivation - X Biomass concentration - V₁ Liquid volume in BS1 - w_SG Superficial gas velocity in BS1 - G Gas holdup in BS1 - ₁ V₁/F_v mean liquid residence time in BS1 - BS1 O₂ absorber column - BS2 O₂ desorber column - D Desmophen (antifoam agent) - NS Nutrient salt solution (Table 1)     

Investigation of the structure of two-phase flow model-media in bubble-column bioreactors

Summary By applying photographic, electrical conductivity, and electrooptical methods, the transverse variation of bubble size and velocity, the local gas hold up, and the local specific gas/liquid interfacial area were estimated in a bench scale bubble-column bioreactor containing model cultivation media. The liquid velocity profile, the transverse turbulence intensity variations, and the turbulence energy dissipation scale were also measured by a hot film turbulence probe and constant temperature anemometer technique.A significant relationship was found between the two-phase flow fluid dynamical state and the transverse variation of the various properties.Symbols M mass - L length - T time - a gas/liquid interfacial area L² - specific gas/liquid interfacial area with regard to the bubbling layer volume L^–1 - D transverse coordinate (measured from the wall of the column) L - d bubble diameter L - d mean bubble diameter L - d_e dynamic equilibrium (maximum stable) bubble diameter L - d_p primary bubble diameter L - d_s Sauter bubble diameter L - E specific energy dissipation rate with regard to the volume of the liquid ML^–1T^–3 - EV_L energy dissipation rate ML²T^–3 - , since =1 g/cm³, E has the same numerical value as E. Therefore, the symbol E is used everywhere in the present paper for E for simplicity and called energy dissipation rate (S.s^–2=Stokes.s^–2) L²T^–3 - E_G or local relative gas holdup - f (r) cross correlation function - g acceleration of gravity LT^–2 - h longitudinal distance from the aerator L - relative turbulence intensity - N_O number of u and crossings T^–1 - n_B bubble frequency T^–1 - r distance between two points 1 and 2 of the cross correlation function L - t time - u instantaneous liquid velocity LT^–1 - mean liquid velocity LT^–1 - mean square fluctuation velocity L²T^–2 - turbulence intensity LT^–1 - w_SG superficial gas velocity LT^–1 - w_SL superficial liquid velocity LT^–1 - or E_G local relative gas holdup LT^–1 - energy dissipation scale L - kinematic liquid viscosity L²T^–1 - liquid density M L^–3 - surface tension M T^–2 - dynamic turbulence pressure M L^–1T^–2 Indices p primary (at the aerator) - e equilibrium (far from the aerator)     

Viscous media in tower bioreactors: Hydrodynamic characteristics and mass transfer properties

Studies in tower reactors with viscous liquids on flow regime, effective shear rate, liquid mixing, gas holdup and gas/ liquid mass transfer (k _La) are reviewed. Additional new data are reported for solutions of glycerol, CMC, PAA, and xanthan in bubble columns with diameters of 0.06, 0.14 and 0.30 m diameter. The wide variation of the flow behaviour index (1 to 0.18) allows to evaluate the effective shear rate due to the gas flow. New dimensionless correlations are developed based on the own and literature data, applied to predict k _La in fermentation broths, and compared to other reactor types.List of Symbols a(a) m^–1 specific interfacial area referred to reactor (liquid) volume - Bo Bond number (g D _c ² _L/) - c _L(c _L ^* ) kmol m^–3 (equilibrium) liquid phase oxygen concentration - C coefficient characterising the velocity profile in liquid slugs - C _s m^–1 coefficient in Eq. (2) - d _B(d_vs) m bubble diameter (Sauter mean of d _B) - d ₀ m diameter of the openings in the gas distributor plate - D _c m column diameter - D _L m²s^–1 diffusivity - E _L(E_W) m² s^–1 dispersion coefficient (in water) - E ² square relative error - Fr Froude number (u _G/(g D_c)^0.5) - g m s^–2 gravity acceleration - Ga Gallilei number (g D _c ³ _L ² / _eff ² ) - h m height above the gas distributor the gas holdup is characteristic for - k Pasⁿ fluid consistency index (Eq. 1) - k _L m s^–1 liquid side mass transfer coefficient - k _La(k_La) s^–1 volumetric mass transfer coefficient referred to reactor (liquid) volume - L m dispersion height - n flow behaviour index (Eq. 1) - P W power input - Re liquid slug Reynolds number ( _L(u _G +u _L) D _c/_eff) - Sc Schmidt number ( _eff/( _L D _L )) - Sh Sherwood number (k _La D _c ² /D_L) - t s time - u _B(u_sw) m s^–1 bubble (swarm) rise velocity - u _G(u_L) m s^–1 superficial gas (liquid) velocity - V(V_L) m³ reactor (liquid) volume Greec Symbols W m^–2 K^–1 heat transfer coefficient - y(y _eff) s^–1 (effective) shear rate - _G relative gas holdup - s relaxation time of viscoelastic liquid - _L(_eff) Pa s (effective) liquid viscosity (Eq. 1) - _L kg m^–3 liquid density - N/m surface tension     

Light dependence of protoplasmic streaming in Nitella flexilis L. as measured by means of laser-velocimetry

Laser-velocimetry was applied in order to study the effect of light on the velocity of protoplasmic streaming (pps) in Characean cells. A change from dark to light (= 6 W · m^–2) leads to an acceleration of streaming by about 15–30% with a time-constant of approx. 300 s. The transition from light to dark causes a transient decrease of velocity below the original dark level. This response occurs with a time constant of about 500 s. It returns to its initial value with a time-constant of about 2000 s. This may indicate that a control loop of cytosolic homeostasis takes a decrease in pCa more seriously than an increase. A possible involvement of temperature effects caused by illumination was excluded by measuring the influence of temperature. Steady-state velocity of streaming changed by 5% per 1° C. Irradiation with infra-red light ( > 780 nm) did not cause a change in velocity. The absence of a light effect on streaming velocity in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) shows that photosynthesis and not phytochrome is involved. The role of light-induced changes of pCa is discussed, especially with respect to the hypothesis of Vanselow and Hansen (1989, J. Membr. Biol. 110, 175–187) that photosynthesis acts on the plasmalemma K⁺-channel via light-induced uptake of Ca²⁺ into the chloroplasts.Abbreviations and Symbols ASF auto structure function - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - pps protoplasmic streaming - _L, _D, _C time-constants of the light and dark responses, and of a putative Ca-control system Financial support by the Deutsche Forschungsgemeinschaft is gratefully acknowledged. The first author was granted a scholarship by the state of Schleswig-Holstein. We are indebted to Prof. Dr. G. Pfister for technical advice and helpful discussions and to Mrs. E. Götting for drawing the figures.