Biologic Transport of Silver Ions!

FREE Information that WORKS!

Those that say silver ions complex with stomach acid to produce mostly useless 
compounds, have not looked at the big picture, of biologic ion transport!

Please note that references are to ions, not metallic atoms, crystals or salts! 
While body electrolytes can release a few ions of silver from metallic silver 
it is far from the benefits of direct intake of billions of silver ions!

Following are brief statements taken from many studies - use your "edit/find" 
function to jump to the links to the full report!

Digestion and absorption begins in the mouth!

Metallic ions, either free or disassociated from dissolved soluble salts are 
both absorbed sublingually and/or isolated by ligands in the saliva, usually 
metalloproteins. Metallothionein (MT) is a relatively small molecule that binds 
heavy metals including silver, cadmium, copper and zinc, and is made by most 
cells in our body. Your saliva has over 200 different proteins and fully one 
third of body proteins are metalloproteins I. E. carrying metallic ions.


Thus, reactive ions (missing one or more electrons) can be transported past the 
stomach and thru the circulatory system without local reactions. Metal ion 
substitution permits even a zinc metalloprotein to take up the silver ion and 
release the zinc ion. The free, ionized zinc, which would be toxic if permitted 
to accumulate, binds to a metal regulatory element on the promoter region of the 
metallothionein gene and "turns on" the synthesis of more metallothionein.


Act on acid anhydrides, Catalysing transmembrane movement of substances!

Silver exporting ATPase Hydrolases: The ion pump mechanism utilizes energy from 
ATP to force ions thru a cell membrane, verses the passive diffusion, in which 
case the protein (on the cell) that allows this transport is called an ion 
channel.

Proteins include: Enzymes, Neurotransmitters and some hormones, antibodies, ion 
channels, receptor sites, etc.

The mammalian form of MT appears to have the principal physiological role of 
providing a homeostatic function for copper and zinc. They are able to 
distribute these metal ions when required for the synthesis of metaldependant 
cellular compounds. They have been referred to as "metal transfer agents" 
because of their role in depositing or removing (Ed: a specific case) zinc from 
zinc-dependant proteins.

Metallothionein (MT) is a relatively small molecule that binds heavy metals 
including silver, cadmium, copper and zinc, and is made by most cells in our 
body. Its production can be induced in the intestinal cells where it is thought 
to help keep us from absorbing a lot of toxic heavy metals such as cadmium. MT 
is also thought to be involved in the regulation of the cellular concentration 
of the essential minerals copper and zinc. 

The lining of our blood vessels is made up of a specific cell type called 
endothelial cells. Whereas the intestinal cell is the first barrier to the 
absorption of minerals, the endothelial cells are the secondary barrier to 
getting minerals into our tissues and organs.


Cells are constantly pumping ions in and out through their plasma membranes. In 
fact, more than half the energy that our bodies consume is used by cells to 
drive the protein pumps in the brain that do nothing else but transport ions 
across plasma membranes of nerve cells. 

How can ions be transported across membranes that are effectively impermeable to 
them? Cells contain proteins that are embedded in the lipid bilayer of their 
plasma membranes and extend from one side of the membrane through to the other. 
Such trans-membrane proteins can function to effect ion transport in several 
ways.


As to the action of silver in the body, while there may be some catalytic 
action, silver ions will adhere to the sulphydral groups on bacterial cell walls 
and thus compromise the action of enzymes and so on, silver has also been found 
bonded to the DNA and RNA of bacterial cells, having presumably disrupted the 
cell wall enough to gain entry. 

Interestingly, it has also been found that if one removes the silver bonded to 
the cell wall of bacteria, that the bacteria is able to revive. Binding of Ag 
ions by Metallothioneins 

 As an extension of the chemistry of metal thiolates, the 
study on the metal-ion binding ability of recombinant MT was undertaken by this 
group about ten years ago. The genetic engineering approach has allowed us to 
express several MT of different species (mouse, drosophila, crustacean, human,.

. . ) as well as their constitutive domains separately with a high purity and 
yield. More recently, the metal binding abilities of these metalloproteins in 
the presence of several metal ions (Zn, Cd, Cu, Ag, Hg, Pb,. . . ) has been 
analyzed and the influence of several factors (pH, stabilization time required, 
temperature, . . . ) considered. 

The quality of the recombinant proteins has provided a deeper insight on the 
behavior of the proteins than that obtained from native or chemically 
synthetized MT. Currently, our efforts are devolved to the role of zinc as a 
structural element in MxZny-MT species, the possible function of MT as a radical 
scavenger and the genesis and differentiation of the MT proteins along the 
evolution of living organisms.

This group is one of the two partners of the Group of Synthesis and Modeling of 
Transition Metal Systems, which has been awarded the qualification of Quality 
Research Group by the CIRIT (Generalitat de Catalunya; Identification number 
1997SGR 00411). 

The group has a well established collaboration with the research groups headed by 
Prof. ~Agust Lleds Falc . uab. es/iqui0/frame_qft. htm (Department of 
Chemistry, Facultat de Ci?ncies, Universitat Autnoma de Barcelona) and by Dr. 
Slvia Atrian i Ventura http://www. bio. ub. es/genet/memoria/mol5uk. htm 
(Department of Genetics, Facultat de Biologia, Universitat de Barcelona), and by 
Dr. William Clegg (Department of Chemistry, University of Newcastle, UK). -- ---
------------ -------------------- Metalloprotein Program Project Overview 
http://www.

scripps. edu/research/metallo/ One-third of all proteins are "metalloproteins", 
chemical combinations of protein atoms (carbon, nitrogen, oxygen, hydrogen, 
sulfur) with ions of metals such as iron, calcium, copper, and zinc. The 
hemoglobin, for example, that carries oxygen in the bloodstream, is an iron-
containing metalloprotein. 

The metal ions in metalloproteins are critical to the protein's function, 
structure, or stability. In fact, numerous essential biological functions 
require metal ions, and most of these metal ion functions involve 
metalloproteins. Thus, metalloproteins make life on Earth possible and the 
ability to understand and ultimately control the binding and activity of protein 
metal sites is of great biological and medical importance.


complex ions, or coordinated complexes as they are also called, generally 
consist of a positively charged central metal atom or ion, like the zinc in 
tetramine zinc, surrounded by electron-donating, or basic, groups called ligands 
; in the tetrammine zinc complex, the NH3 groups are the ligands. The number of 
bonds connecting the ligands to the central atom or ion is its coordination 
number, or ligancy. 

Transition metals (see transition elements ) are especially suited for forming 
complex ions because they have filled or partially filled electron orbitals that 
can participate in bonding the ligands to the metal. The bonding holding the 
ligands to the central atom or ion is similar to covalent bonding between atoms 
but is more complex (see chemical bond ). All the ligands surrounding the 
central ion need not be the same, and some positions can be occupied by solvent 
molecules. Because ligands remain in a fixed position around a central atom or 
ion, in many complexes different isomers , or arrangements, of the ligand groups 
are possible. 

When there are four or more ligands around a central atom, different 
stereoisomers, or spatial configurations, are possible (see stereochemistry ). 
Many complex ions are colored; the specific color of a complex depends on both 
the central atom or ion and the ligands. 

For example, when cobaltous chloride is dissolved in water, a pale pink 
solution, sometimes called invisible ink, results because of the presence of the 
hydrated cobaltous ion, Co(H2O)6+2; this solution does not show up well on 
paper, but if the paper is heated to drive the water off, visibility improves 
because of the formation of a blue tetrachlorocobalt (II)-2 complex. 

Some of the more important complex ions are vitamin B12, chlorophyll, and the 
heme component of hemoglobin, in which the central metal ions are cobalt, 
magnesium, and iron, respectively, and the ligands are complex organic systems. 
Many enzymes contain a metal ion about which parts of the protein are 
coordinated.


Metal-Substituted Metalloproteins http://www. chem. qmw. ac.

uk/iubmb/etp/etp6t11. html#p11 Scientists from several areas, dealing with 
spectroscopy and electron-transfer mechanisms, often use metalloproteins in 
which a metal at the active site has been substituted by another metal ion, like 
Co,Zn, Hg, Cd.


Examples are zinc-substituted cytochromes and cobalt-substituted ferredoxins.


The names for such modified proteins are easily given by using indications like: 
'zinc-substituted . . . . '. In case of multi-metal proteins, where ambiguity 
might arise about which metal has been substituted, one could easily add in 
parentheses the name of the metal that has been replaced, such as: cobalt-
substituted [Fe] nitrogenase.


As to the action of silver in the body, while there may be some catalytic 
action, silver ions will adhere to the sulphydral groups on bacterial cell walls 
and thus compromise the action of enzymes and so on, silver has also been found 
bonded to the DNA and RNA of bacterial cells, having presumably disrupted the 
cell wall enough to gain entry. 

Interestingly, it has also been found that if one removes the silver bonded to 
the cell wall of bacteria, that the bacteria is able to revive.


Some links to papers discussing the role of metallothioneins : http://bssv01.

lancs. ac. uk/StuWork/BIOS316/Bios31698/Mthion/MET. HTM The mammalian form of MT 
appears to have the principal physiological role of providing a homeostatic 
function for copper and zinc. 

They are able to distribute these metal ions when required for the synthesis of 
metaldependant cellular compounds. They have been referred to as "metal transfer 
agents" because of their role in depositing or removing zinc from zinc-dependant 
proteins.


Metallothionein Structure The protein is composed of a polypeptide chain of 61 
amino acid residues of which there are 20 cysteine residues and many lysineês 
and arginines. The amino acid structure of MTs has been highly conserved 
throughout evolution and changes have been conservative with regard to chemical 
and space-filling properties. 

It should also be noted that there are no aromatic amino acids and very few 
bulky aliphatic ones. All the cysteines occur in the reduced forms and the metal 
ions are co-ordinated to them through mercaptide bonds.


Metallothionein (MT) is a relatively small molecule that binds heavy metals 
including silver, cadmium, copper and zinc, and is made by most cells in our 
body. Its production can be induced in the intestinal cells where it is thought 
to help keep us from absorbing a lot of toxic heavy metals such as cadmium. MT 
is also thought to be involved in the regulation of the cellular concentration 
of the essential minerals copper and zinc. 

The lining of our blood vessels is made up of a specific cell type called 
endothelial cells. Whereas the intestinal cell is the first barrier to the 
absorption of minerals, the endothelial cells are the secondary barrier to 
getting minerals into our tissues and organs.


http://www. nal. usda. gov/ttic/tektran/data/000009/46/0000094696. html 
Metallothionein (MT) is a low-molecular-weight protein ubiquitous in the animal 
kingdom (1). MT has an unusual amino acid composition in that it has no aromatic 
amino acids and one-third of its residues are cysteines. These cysteine residues 
bind and store metal ions (2). 

The MT multigene family is composed of at least four isoforms. MT-I and -II 
exist in all tissues, are regulated in a coordinate fashion, and appear 
functionally equivalent (1-3). Other members of the MT gene family, however, 
show different patterns of expression: MT-III is found mainly in brain (4) and 
MT-IV in stratified squamous epithelium (5). 

MT-III and -IV are regulated very differently than MT-I and -II and their 
significance is not yet understood. Evidence also suggests a role for MT in 
protection aginst oxidative stress. 

MT can serve as a sacrificial scavenger for hydroxyl radicals in vitro (35) and 
protect against free radical-induced DNA damage (36-38). MT can also assume the 
function of superoxide dismutase in yeast (39) and protect against lipid 
peroxidation in erythrocyte ghosts produced by xanthine oxidase-derived 
superoxide anion and hydrogen peroxide (40). 


Hepatocytes from MT-null mice are more sensitive than control cells to oxidative 
damage produced by t- butylhydroperoxide and paraquat (41,42). MT is induced by 
oxidative stress- producing chemicals (43) and thus may protect against 
oxidative damage (7) and the toxicity of alkylating anticancer drugs (8).


http://lowdose. org/pubs/ehp/members/klaassenfull. html The proteins of the 
metallothionein superfamily are resposible for primary metal storage, transport 
and detoxification of the cell. Most are found within the cytosol but a few are 
found in the nucleus, especially in mammalian metallothioneins in the ACE1 
complex which is concerned with gene expression. Ag-metallothionein has only 
been found in Saccharomyces Crevisiae to date.


http://bssv01. lancs. ac. uk/StuWork/BIOS316/Bios31699/AgMet/AgMet. html Ag-
Metallothionein The chain wraps around the silver ions so that they are enclosed 
by two parallel loops leaving a cup like cleft where the Ag cluster resides.

Fig. 2 shows the arrangement of the ligand binding residues from infront of(fig.

2a) and behind(fig. 2b) the protein as well as looking at the open cleft(fig.

2c). In Fig. 3a the two parallel loops can be seen at the left and right hand 
sides of the diagram with the open end of the cup facing. Fig. 3b shows a 
spacefill representation of the metallothionein in the same orientation. 

It can be seen from this that the open face of the cup leaves the metal cluster 
slightly exposed. (see pictures there) http://www3. ncbi. nlm. nih. gov/htbin-
post/Entrez/query?db=m&form=6&dopt=r&uid=96159028 3D solution structure of 
copper and silver-substituted yeast metallothioneins. 

For the first 40 residues in both structures, the polypeptide backbone wraps 
around the metal cluster in two large parallel loops separated by a deep cleft 
containing the metal cluster.

Minor differences between the two structures include differences in hydrogen 
bonds and the orientation of the N-terminus with the overall protein volume 
conserved to within 6. 5%.


p://www. thorne. com/altmedrev/fulltext/tox3-4. html A second adaptive and 
protective response to toxic metal exposure is induction of metallothionein 
synthesis.


Metallothioneins are a fascinating group of low molecular weight, intracellular 
proteins that serve as a storage depot for copper and zinc, and "scavenge" 
sulfhydryl-reactive metals that enter the cell. Metallothioneins across species 
are rich in cysteine (~30%) and have higher affinities for Hg and Cd than for 
zinc. 25 Therefore as Hg and Cd bind to metallothionein, and are restricted from 
entering the mitochondria, zinc is released. 

The free, ionized zinc, which would be toxic if permitted to accumulate, binds 
to a metal regulatory element on the promoter region of the metallothionein gene 
and "turns on" the synthesis of metallothionein. 25 Such induction of 
metallothionein provides increased binding capacity for both toxic metals 
(protective) and zinc (functional).


Total uptake of Ag (subcutaneously with (AgNO3)) into the liver was not 
stimulated, but its uptake into the MT fraction increased significantly in the 
LEC rats.


http://link. springer. de/search for Volume 74, Issue 4/5, pp 190-195 in 
Archives of Toxicology l Elemental Composition Cells are 90% water. Of the 
remaining molecules present, the dry weight is approximately: 50% protein 15% 
carbohydrate 15% nucleic acid 10% lipid 10% miscellaneous Total approximate 
composition by element: 60% H 25% O 12% C 5% N Note that these four elements 
make up almost the entire composition of all living organisms. 

The only other notable elements that are significant constituents of biological 
molecules are P, phosphorus, and S, sulfur. In addition, living things use 
traces of sodium, magnesium, chlorine, potassium, calcium, and iron, and even 
less of certain other metals (see Purves page 20). 

Organelles are small structures within cells that perform dedicated functions. 
As the name implies, you can think of organelles as small organs. There are a 
dozen different types of organelles commonly found in eukaryotic cells.


Nucleus This is where the DNA is kept and RNA is transcribed. RNA is transported 
out of the nucleus through the nuclear pores. Proteins needed inside the nucleus 
are transported in through the nuclear pores. 

The nucleolus is usually visible as a dark spot in the nucleus (note the dark 
nucleolus in this electron microscope photo of a nucleus), and is the site of 
ribosome formation.


Ribosomes Ribosomes are the sites of protein synthesis , where RNA is translated 
into protein. Protein synthesis is extremely important to cells, and so large 
numbers of ribosomes are found throughout cells (often numbering in the hundreds 
or thousands). 

Ribosomes exist floating freely in the cytoplasm, and also bound to the 
endoplasmic reticulum (ER). ER bound to ribosomes is called rough ER because the 
ribosomes appear as black dots on the ER in electron microscope photos, giving 
the ER a rough texture. These organelles are quite small, made up of 50 proteins 
and several long RNAs intricately bound together. Ribosomes have no membrane. 
Ribosomes disassemble into two subunits when not actively synthesizing protein.


Mitochondria Mitochondria (singular: mitochondrion) are the sites of aerobic 
respiration, and generally are the major energy production center in eukaryotes.

Mitochondria have two membranes, an inner and an outer, clearly visible in this 
electron microscope photo of a mitochondrion. Note the reticulations, or many 
infoldings, of the inner membrane,

This serves to increase the surface area of membrane on which membrane-bound 
reactions can take place. The existence of this double membrane has led many 
biologists to theorize that mitochondria are the descendants of some bacteria 
that was endocytosed by a larger cell billions of years ago, but not digested. 

This fascinating theory of symbiosis, which might lend an explanation to the 
development of eukaryotic cells, has additional supporting evidence. 
Mitochondria have their own DNA and their own ribosomes; and those ribosomes are 
more similar to bacterial ribosomes than to eukaryotic ribosomes.


Chloroplasts These organelles are the site of photosynthesis in plants and other 
photosynthesizing organisms. They also have a double membrane. There is a more 
complete description of the chloroplast here, in the chapter on photosynthesis.


Endoplasmic Reticulum (ER) The ER is the transport network for molecules 
targeted for certain modifications and specific final destinations, as opposed 
to molecules that are destined to float freely in the cytoplasm. 

There are two types of ER, rough and smooth. Rough ER has ribosomes attached to 
it, and smooth ER does not. Golgi apparatus This organelle modifies molecules 
and packages them into small membrane bound sacs called vesicles.


These sacs can be targeted at various locations in the cell and even to its 
exterior. Lysosome This organelle digests waste materials and food within the 
cell, breaking down molecules into their base components with strong digestive 
enzymes . 

Here we can see an advantage of the compartmentalization of the eukaryotic cell: 
the cell could not support such destructive enzymes if they were not contained 
in a membrane-bound lysosome . http://esgwww. mit.

edu:8001/esgbio/cb/membranes/transport. html The big picture. . . . . . . . . .

. . . . . . . In practice, given the structure of known membrane proteins , 
these holes are only large enough to allow the passage of small molecules 
through the plasma membrane, almost always simple ions like hydrogen, potassium 
or sodium. The ions may pass through the hole or orifice by passive diffusion, 
in which case the protein that allows this transport is called an ion channel.

Alternatively, the transmembrane protein may invest energy, usually derived from 
ATP, to actively force ions from one side of the plasma membrane to the other, 
in which case it will be an ion pump http://esg-www. mit.

edu:8001/esgbio/cb/membranes/proteins. html Cells are constantly pumping ions in 
and out through their plasma membranes. In fact, more than half the energy that 
are bodies consume is used by cells to drive the protein pumps in the brain that 
do nothing else but transport ions across plasma membranes of nerve cells.

How can ions be transported across membranes that are effectively impermeable to 
them? Cells contain proteins that are embedded in the lipid bilayer of their 
plasma membranes and extend from one side of the membrane through to the other.

Such transmembrane proteins can function to effect ion transport in several 
ways. But how can they cope with the energetically highly unfavorable situation 
in which an ion must pass through the hydrophobic inner layers of the plasma 
membrane? 

Domains If we examine the detailed structures of many transmembrane proteins, we 
see that they often have three different domains, two hydrophilic and one 
hydrophobic . 

A hydrophilic domain (consisting of hydrophilic amino acids) at the N-terminus 
is poking out in the extracellular medium, a hydrophobic domain in the middle of 
the amino acid chain, often only 20-30 amino acids long, is threaded through the 
plasma membrane, and a hydrophilic domain at the C-terminus protrudes into the 
cytoplasm. 

The transmembrane domain, because it is made of amino acids having hydrophobic 
side chains, exists comfortably in the hydrophobic inner layers of the plasma 
membrane.


Because these transmembrane domains anchor many proteins in the lipid 
bilayer,these proteins are not freefloating and cannot be isolated and purified 
biochemically without first dissolving away the lipid bilayer with detergents.

(Indeed, much of the washing we do in our lives is necessitated by the need to 
solubilize proteins that are embedded in lipid membranes using detergents! ) 
Cells have ion gates, valve like proteins that permit specific ions to enter!

Some examples of proteins Antibodies: they recognize molecules of invading 
organisms.


Receptors: part of the cell membrane, they recognize other proteins, or 
chemicals, and inform the cell. . . 'The Door Bell'.


Enzymes: assemble or digest.


Neurotransmittors and some hormones: Trigger the receptors. . . (the finger on 
the door bell. . . ) Channels,and pores: holes in the cell membrane (with or 
without a gate). Usually, filter the flow. . .


http://www. iacr. bbsrc. ac. uk/notebook/courses/guide/prot. htm for a review of 
protein structure and diversity!

Huge source list of data on proteins: http://www. iacr. bbsrc. ac.

uk/notebook/links/protein. htm [ LinkDB ] Silver exporting ATPase ENTRY EC 3. 6. 
3. 53 NAME Ag+-exporting ATPase CLASS Hydrolases Acting on acid anhydrides 
Catalysing transmembrane movement of substances SYSNAME ATP phosphohydrolase 
(Ag+-exporting) REACTION ATP + H2O + Ag+(in) = ADP + Orthophosphate + Ag+(out) 
SUBSTRATE ATP H2O Ag+ PRODUCT ADP Orthophosphate COMMENT A P-type ATPase that 
exports Ag+ ions from pathogenic microorganisms as well as from some animal 
tissues.


DBLINKS ExPASy - ENZYME nomenclature database: 3. 6. 3. 53 WIT (What Is There) 
Metabolic Reconstruction: 3. 6. 3. 53 http://www. sph. umich.

edu/eih/heavymetals/Manuscripts/HerrinR. htm (full text) Summary: Results of 
competing ligand equilibration experiments indicate that the majority of Ag(I) 
in the filtered phase of river water and sewage treatment plant effluent is 
strongly complexed to ligands present in those systems.


Furthermore, appreciable fractions of these Ag(I) complexes adsorb to Teflon 
surfaces in unacidified samples.


These complexes do not, however, adsorb to glass surfaces. Oxidation of river 
water and effluent reduce the fraction of Teflon-adsorbed Ag to undetectable 
levels. These observations indicate that Ag(I) in river waters and effluents is 
present in the form of strong complexes that are hydrophobic in nature. Organic 
matter containing thiol functionalities is likely to cause this behavior.

Formation of hydrophobic complexes may enhance the bioavailability of Ag(I).


http://www. sph. umich. edu/eih/heavymetals/Manuscripts/FortinC. htm (full text) 
Summary: Short-term (< 1 h) silver uptake by the green alga Chlamydomonas 
reinhardtii was measured in the laboratory in defined inorganic media in the 
presence or absence of ligands (chloride and thiosulfate). In contradiction to 
the Free-Ion Model of metal uptake, silver accumulation by the alga proved to be 
sensitive to the choice of ligand used to buffer the free silver concentration.

For a low fixed free Ag+ concentration of 10 nM, silver uptake in the presence 
of thiosulfate (0. 11 µM) was 2X greater than in the presence of chloride (4 
mM). When sulfate was removed from the exposure medium, silver uptake in the 
presence of thiosulfate was even more markedly enhanced (more than 4X greater 
than in the presence of chloride). 

Varying the sulfate concentration in the exposure medium only affected silver 
uptake if thiosulfate was present. We conclude that silver-thiosulfate complexes 
are transported across the plasma membrane via sulfate / thiosulfate transport 
systems, and that sulfate acts as a competitive inhibitor of this uptake 
mechanism.


http://www. envsci. rutgers. edu/~reinfldr/ reinfelder@envsci. rutgers. edu 
request source for: Reinfelder, J. R. and S. I. Chang. (1999) Speciation and 
microalgal bioavailability of inorganic silver. Environ. Sci. Technol. 33:1860-
1863 http://www. orgchm. bas. bg/~kaneti/base. html Silver ion chromatography 
has been and still is the core method of lipid analysis. The method is based on 
the distinctive property of unsaturated organic compounds to form weak charge 
transfer complexes with silver ion [1].


Thus, lipid molecules are separated into groups according to the overall number 
of the double bonds in the fatty acid residues.


http://www. google. com/search?q=cache:www. scar. utoronto.

ca/~96wongal/new/silver. pdf+ligand+silver Analysis of Silver in Freshwater and 
Freshwater Sedimentation Introduction Silver (Ag), in its ionic form, is one of 
the most toxic heavy metals, surpassed only by mercury. When presented as silver 
nitrate in laboratory water, Ag is highly toxic to freshwater fish, with median 
lethal concentration (LC50) values between 5 - 60 µg Ag/L. 

1 However, Ag complexed with inorganic cations such as thiosulfate and sulfide 
have been shown to be less toxic by orders of magnitude for both fathead minnows 
(Pimephales promelas) and rainbow trout (Oncorhynchus mykiss). 

2 It is clear that water chemistry plays a crucial role in the toxicity of Ag in 
freshwater species. As a type-B metal cation, Ag+ tends to coordinate and 
complex soft bases such as sulfur, and the high stability constants for 
organosulfurs complexed with silver are indicative of this fact. 

Elevated concentrations of silver are usually associated with industrial 
processes such as mining and photographic processing and Silver found in 
photographic effluents is predominantly discharged as a soluble, undissociated 
silver thiosulfate complex.

During secondary waste treatment, the thiosulfate complexes are converted to 
chemically inert silver sulfide (Ag2S), which is highly insoluble in water 
(solubility coefficient = 310-10 mg/L for natural waters). 

3 As a result, the majority of the silver which is treated is incorporated into 
sludge, which is later shipped away from the treatment plant as solid waste. 
Hence, silver which is discharged to the environment exists in a colloidal or 
particulate phase and is very quickly scavenged by suspended sediments. 

Background aqueous Ag(I) concentrations in freshwater samples are generally very 
low (in units of picomols/L) because of the strong binding of silver with 
sulfur. 4 http://www. google.com/search?q=cache:www. epa. gov/sab/epec0006. pdf+ligand+silver 
Background The Biotic Ligand Model (BLM) is a model that incorporates metal speciation and the 
protective effects of competing cations to predict metal binding at the fish gill or other site of action 
of acute metal toxicity in aquatic organisms (i. e., the "biotic ligand") (Figure 1). 
The Agency has proposed that the BLM be included in an integrated approach to metals management, 
including establishment of metals water quality.