In Vitro Phosphorylation of Proteins in IAA-Treated Mesocotyls in Zea mays

Five-mm sections of elongation zones of Zea mesocotyls wereincubated for designated periods with various concentrationsof IAA. In vitro protein phosphorylation in the soluble fraction(85,000 x g supernatant) prepared from the sections was analyzedby sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The phosphorylation of proteins in the soluble fraction thathad been prepared from sections incubated for 20 min in thepresence of 10{small tilde}^s M IAA was greater than that inthe sections incubated for 20 min without IAA. The amount ofphosphorylation of proteins per protein became higher when higherconcentrations increased (10{small tilde}⁸—10{small tilde}⁵M).The growth of sections incubated in the presence of 10{smalltilde}⁸ M IAA or higher concentrations was greater than thatof sections incubated in the absence of IAA. The promotion ofgrowth by IAA was greater at higher concentrations of IAA. Proteinsin the soluble fraction, prepared from sections incubated for20 min in the presence of 10{small tilde}⁵ M IAA, were phosphorylatedin the presence of either 10 fM cAMP, 10 µM cGMP, 100µM W-7, 100 µM W-5, 20 µM H-7 or 20 µMHA1004. The calmodulin antagonist, W-7, and the inhibitor ofprotein kinase C, H-7, inhibited the phosphorylation of proteinsstimulated by incubation with IAA. These results suggest thatIAA promotes cell elongation via protein phosphorylation thatdepends on calmodulin-dependent protein kinase and protein kinaseC. (Received November 29, 1995; Accepted May 20, 1996)     

Photoproduction and Detoxification of Hydroxyl radicals in Chloroplasts and Leaves and Relation to Photoinactivation of Photosystems I and II

The light-dependent production of hydroxyl radicals (HO{dot})by thylakoids, chloroplasts and leaves of Spinacia oleraceawas investigated using dimethylsulfoxide as HO{dot} trappingagent. Maximum rates of HO{dot} production by thylakoids asindicated by the formation of methane sulfinic acid were observedunder aerobic conditions in the absence of added electron acceptors.They were higher than 2 µmol (mg Chl h)^–1. Saturationof HO{dot} production occurred at the low photon flux densityof 100 µmol m^–2 s^–1. Trapping of HO{dot} bydimethylsulfoxide suppressed, but did not eliminate light-dependentinactivation of PSI and II suggesting that HO{dot} formationcontributed to the photosensitivity of isolated thylakoids.DCMU inhibited HO{dot} formation. Importantly, methylviologendecreased HO{dot} formation in the absence, but stimulated itin the presence of Fe³⁺. In intact chloroplasts, HO{dot} formation became appreciableonly after KCN had been added to inhibit effective H₂O₂ scavengingby ascorbate peroxidase. It was stimulated by ferrisulfate,but not by ferricyanide which does not penetrate the chloroplastenvelope. Infiltrated spinach leaves behaved similar in principleto intact chloroplasts in regard to HO{dot} formation but HO{dot}production was very slow if detectable at all by the formationof methylsulfinic acid indicating effective radical detoxification. HO{dot} formation is interpreted to be the result of a Fenton-typereaction which produces HO{dot} in chloroplasts from H₂O₂ andreduced ferredoxin, when O₂ is electron acceptor in the Mehlerreaction and radical detoxification reactions are inhibited. (Received November 13, 1996; Accepted April 23, 1996)     

Early developmental stages of greasyback shrimp,Metapenaeus ensis (de Haan, 1844) (Crustacea, Decapoda, Penaeidae)

Metapenaeus ensis was spawned and laboratory cultured untilthe post-larval stage to illustrate and describe its embryonicand larval development. Fecundities ranged between 454 000 and689 000 eggs, and {small tilde}99.2% of spawned eggs hatchedafter 12 h and 40 min at 33.5 p.p.t. and 29.0-29.1°C. Sixnaupliar, three protozoeal, three mysis and one post-larvalstages were noted. A minimum of {small tilde}10 days (249 h20 min) from the time of hatching were required to completethe larval stages by subsisting only on Chaeioceros gracilisand Tetraselmis tetrathele at varying temperature and salinityof 28.1-29.8°C and 33.5—34.5 p.p.t., respectively.The embryonic and larval developmental stages of M.ensis aregenerally similar to those of other known penaeid species, exceptfor the size and structure of diagnostic characters, setationof appendages and duration of metamorphoses.     

Short-term changes of protozoan control on autotrophic picoplankton in an oligo-mesotrophic lake

In May 1994, we investigated the short-term development of theplanktonic community in the epi- and metalimnion of an oligo-mesotrophiclake (Piburger See, Tyrol), focusing on trophic links betweenprotists and picoplankton, but also including phyto- and zooplankton.Uptake experiments with fluorescently labelled bacteria (FLB)and picocyanobacteria (FIC) were performed in order to comparethe importance of both prey types as carbon sources for bacterivorousprotists. Heterotrophic nanoflagellates (HNF) were responsiblefor {small tilde}90% of total protozoan picoplanktivory (FLB+ FLC); ciliates accounted for {small tilde}10%. A selectivityindex related to prey density showed that both HNF and ciliatesclearly preferred FLC over FLB. The mean cell size of autotrophic(prokaryotic) picoplankton (APP) was nearly three times larger(0.323 µm³) and much less variable than mean bacterialcell volume (0.122 µm³). Although APP biomass was on averageonly 8.6% of total picoplankton biomass, pico-cyanobacteriaaccounted for a mean 15.9% of total HNF carbon uptake. We calculatedthat total HNF grazing could match potential APP maximum growthrates at the beginning of the study period. A strong decreasein HNF individual clearance rate (CR) on APP was clearly relatedto a fall in the percentage of choanofiagellates (from 75 to{small tilde}10% of the HNF community). A simultaneous decreasein HNF biomass and CR was followed by a steep increase in APPabundance; APP abundance and HNF biomass were highly negativelycorrelated both in the epi- and the metalimnion (r_{1 EM} = –0.879,r_{1 META} = =0.907; P = 0.001). Total rotifer abundance increasedby a factor of 50 within 2 weeks and was also negatively correlatedwith HNF biomass (r_{1 EM} = –0.852, P < 0.001; r_{1 META}= –0.659, P < 0.05). HNF grazing was found to exerta strong short-term control on picocyanobacteria and this linkwas probably broken by an increase in metazooplankton, especiallydue to rotifer predation on HNF.     

Fine structure of cribellate spider silk

Sticky silk from webs of the spiders, Uloborus diversus andFilistata arizoniciis,were examined by election microscopy.The silk of U. diversus contains long fibrils, 200 –300A{ring} in diameter, consisting of an electron-dense centralfilament, 30 –60 A{ring} across, embedded in a lightermatrix. Transverse banding is distinguished in the matrix atintervals from over 200 to less than 50 A{ring}. Similar featuresare observed in the silk of F. arizonicus. Extended fibrilshave an altered structure.     

Water Influx Characteristics and Hydraulic Conductivity for Roots of Agave deserti Engelm.

Various plant and environmental factors influence the hydraulicproperties for roots, which were examined using negative hydrostaticpressures applied to the proximal ends of individual excisedroots of a common succulent perennial from the Sonoran Desert,Agave deserti Engelm. The root hydraulic conductivity, L^p, increasedsubstantially with temperature, the approximately 4-fold increasefrom 0.5°C to 40°C representing a Q¹⁰ of 1.45. Suchvariations in L_p with temperature must be taken into accountwhen modelling water uptake, as soil temperatures in the rootzone of such a shallow-rooted species vary substantially bothdaily and seasonally. At 20°C, L_p was 2.3 x 10^–7 ms^{macron}1MPa^{macron}1for 3-week-old roots, decreasing to abouthalf this value at 10 weeks and then becoming approximatelyhalved again at 6 months. For a given root age, L_p for rainroots that are induced by watering as lateral branches on theestablished roots (which arise from the stem base) was aboutthe same as L_p for established roots. Hence, the conventionalbelief that rain roots have a higher L_p than do establishedroots is more a reflection of root age, as the rain roots tendto be shed following drought and thus on average are much youngerthan are established roots. Unlike previous measurements onroot respiration, lowering the gas-phase oxygen concentrationfrom 21% to 0% or raising the carbon dioxide concentration from0.1% to 2% had no detectable effect on L_p for rain roots andestablished roots. L_p for rain roots and established roots wasdecreased by an average of 11% and 35% by lowering the soilwater potential from wet conditions (_soil=0 kPa) to {macron}40kPa and {macron}80 kPa, respectively. Such decreases in L_p mayreflect reduced water contact between soil particles and theroot surface and should be taken into account when predictingwater uptake by A. deserti. Key words: Gas phase, rain roots, root age, soil, temperature, water potential     

Diurnal vertical migration of Gymnodinium mikimotoi during a red tide in Hoketsu Bay, Japan

The depth, velocity and timing of the vertical migration ofGymnodinium mikimotoi were examined using fluorometric fieldobservations. Gymnodinium mikimotoi can migrate vertically {smalltilde}20 m daily at velocities of {small tilde}2.2 m h^–1     

Localization and Characterization of a Novel 20 kDa Polypeptide in the Chloroplast of the Green Alga Dunaliella salina

Recent work with the green alga Dunaliella salina showed thepresence of a {small tilde}20 kDa chloroplast protein that wasrecognized by polyclonal antibodies raised against the isolatedLHC-II [Webb M.R. and Melis A. (1995) Plant Physiol. 107: 885].In this report, a characterization of the {small tilde}20 kDapolypeptide is presented. It is shown that it is localized inthe chloroplast envelope membrane of D. salina. The abundanceof this protein is constant on a per cell basis and independentof the light regime during cell growth. The {small tilde}20kDa polypeptide is easily degraded to a {small tilde}19 kDaproduct during sample preparation. A limited amino acid sequenceof 21 residues from the free N-terminus of the {small tilde}19kDa product was obtained. On the basis of this partial sequence,it was concluded that the {small tilde}20 kDa polypeptide isnot a degradation product of a known LHC-II but rather a novelprotein. The {small tilde}20kDa polypeptide did not cross-reactwith antibodies raised against the Cbr (carotene biosynthesis-related)gene product and showed a different electrophoretic mobilityfrom the latter. Light-shift experiments suggest that the {smalltilde}20 kDa polypeptide is not an ELIP (early light-inducibleprotein). Possible functions of the {small tilde}20 kDa proteinare discussed. ¹Permanent address: Department of Biochemistry, University oflund, PO Box 124, S-221 00 Lund, Sweden     

THE DIET, PREY SIZE AND CONSUMPTION OF PHILINE ORIENTALIS (OPISTHOBRANCHIA: PHILINIDAE) IN HONG KONG

Philine orientalis occurs on Hong Kong's beaches for {smalltilde}2 months each year, in May and June when it breeds, laysegg capsules and dies. It is believed to have a life span ofone year. Hoi Sing Wan, a sandy beach in the New Territoriesof Hong Kong is dominated at lower levels by the venerid bivalveTapes philippinarum, the population of which in May and June,following spring recruitment, mostly comprises juveniles. P.orientalis, occurring at a density of {small tilde} 1.m^–2,feeds voraciously upon these juveniles consuming, in laboratoryexperiments, a mean of 25.day^–1. At Hoi Sing Wan, P. orientalisappears to be highly prey specific. It is, however, known tofeed on other prey items and probably has a catholic diet, duringits annual migration from deeper to shallower sediments, accordingto the prevailing fauna. In terms of wet weight, P. orientalis consumes a mean of {smalltilde}4.4% (2.2–6.7%) of its body weight day^–1.In terms of dry weight, however, this figure increases to amean of 35.5% and one figure of 208% has been recorded. Althoughthis is because of the large body fluid content of this, essentiallyshell-less, gastropod, using a hydrostatic skeleton to achieveburrowing, such figures further attest to the voracity of thebreeding adults. This study joins others in questioning ourpresent understanding of the scale of energy budgets on suchshores, i.e., are our estimates of loss to predation grosslyunderestimated? ^*Present address: Department of Biology, Baptist College, WaterlooRoad, Kowloon, Hong Kong. (Received 20 May 1989; accepted 3 July 1989)     

The annual cycle of Mesodinium rubrum in the waters surrounding the Isles of Shoals, Gulf of Maine

Mesodinium rubrum was collected in Kemmerer bottles, fixed inBouin's solution and protargol stained. Cell volume showed aseasonal change of over an order of magnitude, being largest(3.25x10⁴ µm³) in the early spring and smallest in thesummer. Cell abundance was highest in the spring and lowestin the summer. Biomass followed a similar trend ranging from{small tilde}1 to 147 J m^–3 Production, estimated by amultiple regression that incorporated ambient temperature andcell volume, was 2.5 kJ m^–3 day^–1 This is {smalltilde}0.3% of the primary production.     

Grazing and food size selection by crustacean zooplankton compared to production of bacteria and phytoplankton in a shallow Norwegian mountain lake

Food size selection by suspension-feeding crustaceans in a shallowmountain lake was investigated with radiolabelled algae andbacteria, and with a series of monodisperse fluorescent latexbeads with diameters ranging from 0.25 to 5.18 µm. JuvenileDaphnia longispina was a more efficient grazer on bacteria-sizedparticles than adults. Bosmina longispina and Cyclops scutiferwere both able to ingest bacteria-sized food particles. Thecrustaceans harvested {small tilde} 100% of the primary productionduring the day investigated, but only 20% of the bacterial production.To keep the bacterial biomass in or near steady state, the microzooplanktonmust be harvesting most of the bacterial production.     

Utilization of limiting concentrations of ortho-phosphate and production of extracellular organic phosphates in cultures of marine diatoms

The utilization of ortho-phosphate by two coastal marine diatomspecies, Nitzschia closterium and Cyclotella cryptica, was studiedin batch cultures. The hypothesis was tested that thresholdconcentrations in the phosphate uptake determine the lower limitof environmental phosphate, permitting the existence of species.The turn-over time of residual medium phosphate in culturesis {small tilde}10 min, indicating a rapid equilibration ofconcentration dependent on uptake with leakage of ortho-phosphate.Increasing phosphate starvation in cultures diminished the residualortho-phosphate in the range of {small tilde}60–<2nmol l^–1, as measured radiochemically after elution onSephadex® G-10 gel. These concentrations encompass the rangeof limiting phosphate concentration in continuous cultures ofthe few microalgae, for which these concentrations are actuallymeasured. The diatoms excreted {small tilde}20–100 nmolI^–1 of organic phosphate. One dominating compound, probablyan unusual nucleotide, was incompletely or not resorbed underphosphate starvation. In contrast, Nitzschia closterium excretedunder ample phosphate supply a series of three related compounds,probably phospholipids, that were resorbed under depletion.The association of the organic phosphates with macromolecularexudates is interpreted, along with the other observations,as an indication for a hardly explored periplasmatic phosphatemetabolism in these algae. ³Dedicated to Prof. Dr. H.-A. von Stosch in honour of his 75thbirthday. ⁴This study was conducted at the University of Marburg undersupport of the Humboldt Foundation Publication no. 64 of theproject "Biological Research of the Eems-Dollard Estuary".     

Membrane Potentials of Heterotrophically Cultured Tobacco Cells

The electrophysiological properties of the membrane of Nicotianatabacum var. Sarnsun cultured cells were determined using amicroelectrode technique in standard medium containing 1 mMKC1, 1 mM NaCl and 1 mu CaCl₂ at pH 7. Tobacco callus was derivedfrom the pith (E_m=–104.4%16.2 mV). The membrane potentialsof the callus cells did not show a symmetrical Gaussian distributionbut were scattered over a wide range. The percentage of highmembrane potential cells increased as the subculture was continueduntil about 11 months and then decreased. The response of themembrane potential to electric stimulus, ionic composition,metabolic inhibitors, sugars and amino acids was characteristicof high (E_m=–{small tilde}–160 220 mV; H-cells)and low (E_m=–80{small tilde}–90 mV; L-cells) membranepotential cells. The membrane potential of H-cells was largelydepolarized by addition of CN^–, carbonium cyanide m-chlorophenylhydrazone,decyclohexylcarbodiimide, and triphenyltin chloride and transientlydepolarized by addition of glucose, galactose, mannose or sucrose,and D-alanine, L-alanine or Llysine, but the membrane potentialof L-cells was not. (Received December 3, 1982; Accepted March 16, 1983)     

An Optical Model for Phototactic Orientation in Dictyostelium discoideum Slugs

The optical properties of an enlarged optical model of the tipof a slug (a glass tube filled with sucrose solution) of Dictyosteliumdiscoideum were studied to validate the hypothesis that theorganism orients itself with respect to lateral light usinga lens effect: Light is focussed by refraction onto the distalside of the slug where the higher "signal" compared to the frontside causes a turn toward the light. Light was effectively focusedeven when the model deviated only as little as 10° fromthe light direction. Slugs of D. discoideum strains HO596 and HO813 show bidirectionalphototaxis: They orient themselves at some angle on either sideof the incident light beam. This angle is {small tilde}80°in HO596 and {small tilde}70° in HO813. We suggest thatthis phenomenon can be explained by the optical properties ofthe slug such as absorption and scattering, shape of the tipor location and extension of the light-sensitive zone. The angleof orientation with respect to light is regulated by a balancebetween a turn toward and a turn away from the light direction. (Received October 15, 1985; Accepted February 10, 1986)     

Purification of NADP-Malic Enzyme and Phosphoenolpyruvate Carboxylase from Sugar Cane Leaves

A procedure is described for the purification of phosphoenolpyruvatecarboxylase (EC 4.1.1.31 [EC] ) and NADP-dependent malic enzyme (EC1.1.1.40 [EC] ) from sugar cane leaves. Each enzyme was purified tohomogeneity as judged by sodium dodecyl sulfate-polyacrylamidegel electro-phoresis, with about 30% yield. Phosphoenolpyruvatecarboxylase was purified 54-fold. A molecular weight of 400,000and a homotetrameric structure were determined for the nativeenzyme. The purified carboxylase had a specific activity of20.0 {diaeresis}mol (mg protein)_–1 min_–1, and wasactivated by glucose-6-phosphate and inhibited by L-malate.K_m values at pH 8.0 for phosphoenolpyruvate and bicarbonatewere 0.25 and O.l0 mM, respectively. NADP-malic enzyme, 356-foldpurified, exhibited a specific activity of 71.2 {diaeresis}mol(mg protein)_–1 min_–1 and was characterized as ahomotetramer with native molecular weight of 250,000. Purifiedmalic enzyme showed an absolute specificity for NADP⁺ and requireda divalent metal ion for activity. K_m values of 0.33 and 0.008mM for L-malate and NADP⁺, respectively, were determined. Thisenzyme was inhibited by several organic acids, including ketoand amino acids; while succinate and citrate increased the enzymeactivity when assayed with 10{diaeresis}M L-malate. The effectsshown by amino acids and by citrate were dependent on pH, beinghigher at pH 8.0 than at pH 7.0. (Received October 26, 1988; Accepted February 3, 1989)     

Energetics and feeding dynamics of Euphausia superba in the South Georgia region during the summer of 1994

Measurements of adult Antarctic krill (Euphausia superba) gutcontents, evacuation and egestion rates, as well as digestiveefficiency, were carried out during February-March 1994 in thevicin ity of South Georgia to estimate in situ daily ration.These were combined with acoustically derived biomass data tocalculate the grazing impact of Antarctic krill and its contributionto the carbon flux in the region. Individual levels of gut pigmentconcentrations and evacuation rates ranged from 27 to 1831 ngchlorophyll a-eq. ind.^–1 and from 0.133 to 0.424 h^–1,respectively. Losses of pigment fluor escence during digestionwere very high, ranging from 58 to 98% of the total pigmentdigested. Daily carbon consumption estimated using the gut fluorescencemethod varied from 0.234 to 0.931 mg C ind.^–1 day^–1(or 0.4–1.7% of body carbon), compared to {small tilde}2.73mg C ind.^–1 day^–1 (or {small tilde}5% of body carbon)using the faecal pellet production data. The 3-fold higher dailyration estimated using egestion rate data may be explained bypredation on micro-and mesozooplankton. Maximum krill grazingimpact ranged from 0.4 to 1.9% of the total phytoplankton stockor from 10 to 59% of the total daily primary production. However,grazing impact on the microphytoplankton (>20 µm) wassubstantially higher, at times exceeding 100% of the daily microphytoplanktonproduction. It is suggested that to meet its energetic demands,kriil must consume a substantial proportion of heterotrophiccarbon. ³Present address Zoology Department, University of Fort Hare,P/Bag X1314, Alice, 5700, South Africa     

Modification of the data-processing method for the turbidimetric bioassay of nisin

The data processing method of the turbidimetric bioassay of nisin was modified to facilitate its industrial application. The influence of the initial indicator concentration was minimized by a redefined specific dose of the bacteriocin as the quotient between the titer of the added bacteriocin and the initial population density of the indicator in the suspension. It was found that d _c = 0.125 μg ml⁻¹ was the critical dose of nisin that can cause a complete inhibition of the indicator, Pediococcus acidilactici UL5, with an initial OD of 0.135. To eliminate the interference of the cell debris, an equation, , exploiting d _c, was formulated to obtain the intrinsic survival proportion. The use of the specific dose of the bacteriocin and the intrinsic survival proportion as parameters of the dose/response curve greatly enhanced its repeatability and feasibility. A dual-dosage approach was developed to further simplify the conventional standard dose/response curve method.     

Electrophysiological studies of chemoreceptors sensitive to pyridine on the crayfish walking leg. II. Characteristics of inhibitory molecules

The effect of substituted pyridines on the response of singlepyridine-sensitive cells from crayfish walking legs was investigatedelectrophysiologically. Seven p-substituted pyridines, actingreversibly, were identified as specific antagonists at the pyridinereceptor. The maximum saturation frequency of the response toagonists was reached in the presence of antagonists but thedose–response curves of the agonists were shifted in parallelto the right along the concentration axis. Schild plots of threehighly effective antagonists with six agonists were linear witha slope close to one, indicating competitive antagonism. Theinhibition constants yielded a K₁ value of {small tilde}4–8µmol for the most effective antagonist, 4-(4-nitrobenzyl)pyridine,which had only one order of magnitude lower affinity than themost effective agonist 2,3'-bipyridyl. The antagonists 2,4'-bipyridyland 4-benzylpyridine had K¹ values of 6–10 µmol,followed by 4-acetylpyridine with a K¹ value of 30–70µmol. The rank order of inhibitory potency of the differentantagonists was found to be the same for all units tested. Comparingelectronic effects (Hammett values and pKa values) of the substitutentsin p- and m-position showed that inhibitory effectiveness decreasedwith a decrease in pKa and an increase in Partition coefficientswere determined for 10 agonists and the antagonists which weregenerally more lipophilic than the agonists. A hypotheticalreceptor site is proposed.     

Predator-prey interactions: is 'ecological stoichiometry' sufficient when good food goes bad?

The dietary value of a prey type varies with its nutritionalstatus and hence with its C:N:P content. However, while stoichiometricdifferences between a heterotroph and its food must affect growthefficiency (GE), and thence trophic dynamics, other factorsrelated to food quality may act as powerful modulators of predator–preyinteractions. Thus, minor changes in prey stoichiometry canbe associated with more significant changes in prey quality(production of toxins, mucus, thicker walls etc.) that may havea disproportionate effect on predation rates and GE. We termthe predator response to such events, ‘stoichiometricmodulations’. Often these modulations are negative, decreasingpredation and assimilation rates. We suggest that due considerationshould be given in the construction of multinutrient-based modelsof predators to the processes of prey selectivity, ingestionand digestion as functions of food quality with quantity. Written responses to this article should be submitted to RogerHarris at rph{at}pml.ac.uk within two months of publication. Forfurther information, please see the Editorial ‘Horizons’in Journal of Plankton Research, Volume 26, Number 3, Page 257     

Phy-X/ZeXTRa: a software for robust calculation of effective atomic numbers for photon,electron, proton,alpha particle,and carbon ion interactions

The purpose of the present work is robust calculation of effective atomic numbers ($${Z}_{\text{eff}}$$s) for photon, electron, proton, alpha particle and carbon ion interactions through the newly developed software, Phy-X/ZeXTRa (Zeff of materials for X-Type Radiation attenuation). A pool of total mass attenuation and energy absorption coefficients (for photons) and total mass stopping powers (for charged particles) for elements was constructed first. Then, a matrix of interaction cross sections for elements Z = 1–92 was constructed. Finally, effective atomic numbers were calculated for any material by interpolating adjacent cross sections through a linear logarithmic interpolation formula. The results for $${Z}_{\text{eff}}$$ for photon interaction were compared with those calculated through Mayneord’s formula, which suggests a single-valued $${Z}_{\text{eff}}$$ for any material for low-energy photons for which photoelectric absorption is the dominant interaction process. The single-valued $${Z}_{\text{eff}}$$ was found to agree well with that obtained by other methods, in the low-energy region. In addition, $${Z}_{\text{eff}}$$ values of various materials of biological interest were compared with those obtained experimentally at 59.54 keV. In general, the agreement between values calculated with Phy-X/ZeXTRa and Auto-Zeff and those measured were satisfactory. A comparison of $${Z}_{\text{eff}}$$ values for photon energy absorption calculated with Phy-X/ZeXTRa and literature values for a nucleotide base, adenine, was made, and the relative difference (RD) in $${Z}_{\text{eff}}$$ between Phy-X/ZeXTRa and literature values was found to be 2% < RD < 11%, at low photon energies (1–100 keV), while it was less than 1% at energies higher than 100 keV. Highest $${Z}_{\text{eff}}$$ values were observed at low photon energies, where photoelectric absorption dominates photon interaction. For electrons, corresponding RD(%) values in $${Z}_{\text{eff}}$$ were found to be in the range 0.4 ≤ RD(%) ≤ 1.7, while for heavy charged particle interactions it was 2.4 ≤ RD(%) ≤ 4.2 for total proton interaction and 0 ≤ RD(%) ≤ 8 for total alpha particle interaction. In view of the importance of $${Z}_{\text{eff}}$$ for identifying and differentiating tissues in diagnostic imaging as well as for estimating accurate dose in radiotherapy and particle-beam therapy, Phy-X/ZeXTRa could be used for fast and accurate calculation of $${Z}_{\text{eff}}$$ in a wide energy range for both photon and charged particle (electrons, protons, alpha particles and C ions) interactions.